UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM N-Q

QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED
MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number 811- 21287

John Hancock Preferred Income Fund III
(Exact name of registrant as specified in charter)

601 Congress Street, Boston, Massachusetts 02210
(Address of principal executive offices) (Zip code)

Alfred P. Ouellette, Senior Attorney and Assistant Secretary

601 Congress Street

Boston, Massachusetts 02210

(Name and address of agent for service)

Registrant's telephone number, including area code: 617-663-4324

Date of fiscal year end:  May 31 
Date of reporting period:  August 31, 2006 

ITEM 1. SCHEDULE OF INVESTMENTS




John Hancock           
Preferred Income Fund III           
Securities owned by the Fund on           
August 31, 2006 (unaudited)           
 
  Interest  Maturity  Credit  Par value   
Issuer, description  rate (%)  date  rating (A)  ($000)  Value 

Bonds 6.61%          $70,736,494 
(Cost $71,403,221)           
 
Automobile Manufacturers 0.20%          2,162,675 

Ford Motor Co.,           
Note  7.450  07-16-31  B+  2,755  2,162,675 
Consumer Finance          3,032,070 

General Motors Acceptance Corp.,           
Bond  8.000  11-01-31  BB  3,000  3,032,070 
Electric Utilities 3.53%          37,782,335 

Black Hills Corp.,           
Note  6.500  05-15-13  BBB-  15,000  15,111,735 
DPL, Inc.,           
Sr Note  6.875  09-01-11  BB  5,036  5,277,874 
Entergy Gulf States, Inc.,           
1st Mtg Bond  6.200  07-01-33  BBB+  15,000  14,117,115 
Kentucky Power Co.,           
Sr Note, Ser D  5.625  12-01-32  BBB  3,565  3,275,611 
Integrated Oil & Gas  0.51%          5,459,755 

Amerada Hess Corp.,           
Note  7.125  03-15-33  BBB-  5,000  5,459,755 
Multi-Utilities 1.06%          11,293,500 

DTE Energy Co.,           
Sr Note  6.375  04-15-33  BBB-  7,500  7,373,962 
TECO Energy, Inc.,           
Note  7.000  05-01-12  BB  3,810  3,919,538 
Oil & Gas Refining & Marketing 1.03%          11,006,159 

Valero Energy Corp.,           
Note  7.500  04-15-32  BBB-  9,500  11,006,159 
      Credit  Par value   
Issuer, description, maturity date      rating (A)  ($000)  Value 
Capital preferred securities 8.63%          $92,350,188 
(Cost $96,844,716)           
 
Diversified Banks 3.21%          34,322,500 

Credit Agricole Preferred Funding Trust,           
7.00%, 01-29-49      A  9,000  9,135,000 
Lloyds TSB Bank Plc, 6.90%, 11-29-49 (United           
Kingdom)      A+  25,000  25,187,500 

Page 1


John Hancock       
Preferred Income Fund III       
Securities owned by the Fund on       
August 31, 2006 (unaudited)       
 
Electric Utilities 0.62%      6,629,625 

DPL Capital Trust II, 8.125%, 09-01-31  BB-  6,225  6,629,625 
Gas Utilities 1.22%      13,106,001 

KN Capital Trust I, 8.56%, Ser B, 04-15-27  BB+  8,735  8,560,300 
KN Capital Trust III, 7.63%, 04-15-28  BB+  4,960  4,545,701 
Integrated Telecommunication Services 1.41%      15,112,065 

TCI Communications Financing Trust III,       
9.65%, 03-31-27  BBB-  14,210  15,112,065 
Investment Banking & Brokerage 0.94%      10,025,000 

HBOS Capital Funding L.P., 6.85%, 03-29-49       
(United Kingdom)  A  10,000  10,025,000 
Multi-Utilities 0.90%      9,577,121 

Dominion Resources Capital Trust I, 7.83%,       
12-01-27  BB+  9,097  9,577,121 
Other Diversified Financial Services 0.33%      3,577,876 

JPM Capital Trust I, 7.54%, 01-15-27  A-  3,447  3,577,876 
Issuer    Shares  Value 
Common stocks 4.30%      $46,072,920 
(Cost $33,950,446)       
 
Electric Utilities 0.78%      8,363,468 

FPL Group, Inc.    129,000  5,734,050 
Scottish Power Plc, American Depositary       
Receipt (ADR) (United Kingdom)    55,555  2,629,418 
Gas Utilities 0.31%      3,351,342 

ONEOK, Inc.    87,571  3,351,342 
Independent Power Producers & Energy Traders  1.67%      17,889,810 

TXU Corp.    270,198  17,889,810 
Multi-Utilities 1.54%      16,468,300 

CH Energy Group, Inc.    20,600  1,011,872 
DTE Energy Co.    281,516  11,750,478 
TECO Energy, Inc.    235,000  3,705,950 

Page 2


John Hancock       
Preferred Income Fund III   
Securities owned by the Fund on       
August 31, 2006 (unaudited)   
     
 
  Credit     
Issuer, description  rating (A)  Shares  Value 

Preferred stocks  80.38%      $860,026,983 
(Cost $884,295,022)       
 
Agricultural Products  1.45%      15,532,978 

Ocean Spray Cranberries, Inc., 6.25%,       
Ser A (S)  BB+  195,000  15,532,978 
 
Asset Management & Custody Banks 0.38%      4,052,888 

BNY Capital V, 5.95%, Ser F  A-  170,361  4,052,888 
 
Automobile Manufacturers 2.34%      24,985,316 

Ford Motor Co., 7.50%  B+  761,385  14,161,761 
General Motors Corp., 7.25%, Ser 07-15-41  B-  50,641  904,448 
General Motors Corp., 7.375%, Ser 05-15-48  Caa1  558,194  9,919,107 
 
Broadcasting & Cable TV 0.29%      3,077,833 

Comcast Corp., 7.00%  BBB+  119,900  3,077,833 
 
Consumer Finance 2.40%      25,721,462 

Ford Motor Credit Co., 7.60%  Ba3  25,000  552,250 
HSBC Finance Corp., 6.36%, Depositary Shares,       
Ser B  A  250,000  6,385,000 
HSBC Finance Corp., 6.875%  AA-  636,118  16,240,093 
SLM Corp., 6.00%  A  64,195  1,533,619 
SLM Corp., 6.97%, Ser A  BBB+  18,800  1,010,500 
 
Diversified Banks 7.22%      77,286,300 

BAC Capital Trust II, 7.00%  A  94,600  2,377,298 
BAC Capital Trust III, 7.00%  A  22,000  558,580 
BAC Capital Trust IV, 5.875%  A  411,400  9,709,040 
Fleet Capital Trust VII, 7.20%  A  76,004  1,931,262 
Royal Bank of Scotland Group Plc, 5.75%,       
Ser L (United Kingdom)  A  960,000  23,116,800 
Santander Finance Preferred SA Unipersonal,       
6.41%, Ser 1 (Spain)  A-  100,000  2,525,000 
USB Capital IV, 7.35%  A  59,100  1,491,093 
USB Capital V, 7.25%  A  60,700  1,544,208 
USB Capital VIII, 6.35%, Ser 1  A  269,700  6,661,590 
USB Capital X, 6.50%  A  85,000  2,117,350 
Wachovia Preferred Funding Corp., 7.25%, Ser A  A-  674,800  18,867,408 
Wells Fargo Capital Trust IV, 7.00%  A+  177,800  4,461,002 
Wells Fargo Capital Trust VII, 5.85%  A+  81,700  1,925,669 
 
Electric Utilities 11.93%      127,599,503 

Cleveland Electric Financing Trust I, 9.00%  BB+  27,400  709,386 
Consolidated Edison, Inc., $5.00, Ser A  BBB+  30,000  2,617,500 
Consolidated Edison, Inc., 7.25%  A2  56,000  1,440,880 
DTE Energy Trust II, 7.50%  BB+  36,600  934,398 
Entergy Mississippi, Inc., 7.25%  A-  113,668  2,904,217 

Page 3


John Hancock       
Preferred Income Fund III  
Securities owned by the Fund on         
August 31, 2006 (unaudited)   
     
 
FPC Capital I, 7.10%, Ser A  BB+  746,700  18,794,439 
FPL Group Capital Trust I, 5.875%  BBB+  490,000  11,515,000 
Georgia Power Capital Trust V, 7.125%  BBB+  156,100  3,978,989 
Georgia Power Co., 6.00%, Ser R  A  730,000  18,023,700 
Great Plains Energy, Inc., 8.00%, Conv  BBB-  685,400  16,792,300 
HECO Capital Trust III, 6.50%  BBB-  130,000  3,313,700 
Interstate Power & Light Co., 7.10%, Ser C  BBB-  354,900  9,116,494 
Interstate Power & Light Co., 8.375%, Ser B  Baa3  54,500  1,648,625 
Northern States Power Co., 8.00%  BBB-  84,550  2,191,536 
PPL Electric Utilities Corp., 6.25%,       
Depositary Shares  BBB  130,000  3,331,250 
PPL Energy Supply, LLC, 7.00%  BBB  547,370  13,963,409 
Southern California Edison Co., 6.00%  BBB-  30,000  2,921,250 
Southern California Edison Co., 6.125%  BBB-  20,000  1,966,250 
Virginia Power Capital Trust, 7.375%  BB+  447,600  11,436,180 
 
Gas Utilities 3.33%      35,620,012 

Laclede Capital Trust I, 7.70%  BBB+  82,000  2,077,880 
Southern Union Co., 7.55%, Ser A  BB+  449,000  11,651,550 
Southwest Gas Capital II, 7.70%  BB  810,250  20,953,065 
Vectren Utility Holdings, Inc., 7.25%  A-  37,100  937,517 
 
Hotels, Resorts & Cruise Lines 0.28%      3,014,812 

Hilton Hotels Corp., 8.00%  BB  118,600  3,014,812 
 
Integrated Telecommunication Services 2.61%      27,909,843 

Telephone & Data Systems, Inc., 6.625%  A-  462,900  11,317,905 
Telephone & Data Systems, Inc., 7.60%, Ser A  A-  492,976  12,373,698 
Verizon New England, Inc., 7.00%, Ser B  A3  166,400  4,218,240 
 
Investment Banking & Brokerage 9.35%      100,068,348 

Fleet Capital Trust IX, 6.00%  A  469,200  11,354,640 
Goldman Sachs Group, Inc., 6.20%, Ser B  A-  240,000  6,165,600 
Lehman Brothers Holdings Capital Trust III,       
6.375%, Ser K  A-  793,400  19,866,736 
Lehman Brothers Holdings, Inc., 5.67%,       
Depositary Shares, Ser D  A-  142,500  6,904,125 
Merrill Lynch Preferred Capital Trust III,       
7.00%  A-  417,017  10,642,274 
Merrill Lynch Preferred Capital Trust IV,       
7.12%  A-  232,700  5,966,428 
Merrill Lynch Preferred Capital Trust V, 7.28%  A-  373,700  9,660,145 
Morgan Stanley Capital Trust III, 6.25%  A-  764,025  18,550,527 
Morgan Stanley Capital Trust IV, 6.25%  A-  393,925  9,702,373 
Morgan Stanley Capital Trust VI, 6.60%  A-  50,000  1,255,500 
 
Life & Health Insurance 5.24%      56,073,268 

Lincoln National Capital VI, 6.75%, Ser F  A-  304,000  7,776,320 
MetLife, Inc., 6.50%, Ser B  BBB  1,108,850  28,331,117 
Phoenix Cos., Inc. (The), 7.45%  BBB  531,949  13,362,559 
PLC Capital Trust IV, 7.25%  BBB+  141,400  3,595,802 
PLC Capital Trust V, 6.125%  BBB+  83,300  1,949,220 
Prudential Plc, 6.50% (United Kingdom)  A-  41,500  1,058,250 

Page 4


John Hancock       
Preferred Income Fund III   
Securities owned by the Fund on      
August 31, 2006 (unaudited)   
     
 
 
Multi-Line Insurance 3.86%      41,289,379 

Aegon NV, 6.375% (Netherlands)  A-  241,265  6,026,800 
Aegon NV, 6.50% (Netherlands)  A-  138,850  3,490,689 
ING Groep NV, 7.05% (Netherlands)  A  603,970  15,304,600 
ING Groep NV, 7.20% (Netherlands)  A  641,000  16,467,290 
 
Multi-Utilities 6.71%      71,787,383 

Aquila, Inc., 7.875%  B2  218,707  5,458,927 
Avista Corp., $6.95, Ser K  BB-  138,517  13,990,217 
BGE Capital Trust II, 6.20%  BBB-  668,928  15,913,797 
DTE Energy Trust I, 7.80%  BB+  202,800  5,191,680 
PNM Resources, Inc., 6.75%, Conv  BBB-  273,199  14,069,748 
PSEG Funding Trust II, 8.75%  BB+  462,275  12,222,551 
Public Service Electric & Gas Co., 5.05%,       
Ser D  BB+  30,000  2,760,000 
TECO Capital Trust I, 8.50%  B  85,845  2,180,463 
 
Oil & Gas Exploration & Production 4.20%      44,885,851 

Apache Corp., 5.68%, Depositary Shares, Ser B  BBB  27,500  2,703,594 
Chesapeake Energy Corp., 6.25%, Conv (G)  B+  6,330  1,699,605 
Devon Energy Corp., 6.49%, Ser A  BB+  25,250  2,577,868 
Nexen, Inc., 7.35% (Canada)  BB+  1,494,079  37,904,784 
 
Other Diversified Financial Services 9.08%      97,187,111 

ABN AMRO Capital Funding Trust V, 5.90%  A  867,400  20,635,446 
ABN AMRO Capital Funding Trust VI, 6.25%  A  353,900  8,996,138 
Citigroup Capital VII, 7.125%  A  28,042  704,976 
Citigroup Capital VIII, 6.95%  A  241,200  6,128,892 
Citigroup Capital IX, 6.00%  A  264,800  6,437,288 
Citigroup Capital X, 6.10%  A  720,000  17,791,200 
General Electric Capital Corp., 5.875%  AAA  325,930  7,845,135 
General Electric Capital Corp., 6.10%  AAA  94,747  2,345,936 
JPMorgan Chase Capital XI, 5.875%, Ser K  A-  1,030,000  24,205,000 
JPMorgan Chase Capital XIV, 6.20%, Ser N  A-  25,000  614,500 
JPMorgan Chase Capital XVI, 6.35%  A-  60,000  1,482,600 
 
Real Estate Investment Trusts 5.00%      53,534,232 

Duke Realty Corp., 6.50%, Depositary Shares,       
Ser K  BBB  151,600  3,706,620 
Duke Realty Corp., 6.60%, Depositary Shares,       
Ser L  BBB  118,500  2,909,175 
Duke Realty Corp., 6.625%, Depositary Shares,       
Ser J  BBB  638,100  15,697,260 
Kimco Realty Co., 6.65%, Depositary Shares,       
Ser F  BBB+  384,750  9,772,650 
Public Storage, Inc., 6.18%, Depositary       
Shares, Ser D  BBB+  20,000  473,400 
Public Storage, Inc., 6.50%, Depositary       
Shares, Ser W  BBB+  450,000  11,074,500 
Public Storage, Inc., 7.50%, Depositary       
Shares, Ser V  BBB+  184,530  4,755,338 

Page 5


John Hancock           
Preferred Income Fund III           
Securities owned by the Fund on           
August 31, 2006 (unaudited)           
 
Public Storage, Inc., 7.625%, Depositary           
Shares, Ser T      BBB+  25,500  648,720 
Public Storage, Inc., 8.00%, Depositary           
Shares, Ser R      BBB+  177,100  4,496,569 
Regional Banks 2.47%          26,442,550 

National Commerce Capital Trust II, 7.70%      A-  86,800  2,227,288 
PFGI Capital Corp., 7.75%      A  926,900  24,215,262 
Reinsurance 0.27%          2,840,994 

RenaissanceRe Holdings Ltd., 6.08%, Ser C           
(Bermuda)      BBB  127,800  2,840,994 
Specialized Finance 0.49%          5,289,150 

CIT Group, Inc., 6.35%, Ser A      BBB+  70,000  1,802,500 
Repsol International Capital Ltd., 7.45%,           
Ser A (Cayman Islands)      BB+  137,000  3,486,650 
Thrifts & Mortgage Finance 1.19%          12,736,930 

Abbey National Plc, 7.25% (United Kingdom)      A  163,265  4,109,380 
Abbey National Plc, 7.375% (United Kingdom)      A  339,000  8,627,550 
Wireless Telecommunication Services  0.29%          3,090,840 

United States Cellular, 7.50%      A-  119,800  3,090,840 
  
  Interest  Maturity  Credit  Par value   
Issuer, description, maturity date  rate (%)  date  rating (A)  ($000)  Value 

Short-term investments 0.08%          $811,000 
(Cost $811,000)           
 
Government U.S. Agency 0.08%          811,000 

Federal Home Loan Bank,           
Discount Note  4.95  09-01-06  AAA  811  811,000 
 
Total investments 100.00%          $1,069,997,585 

Page 6


John Hancock
Preferred Income Fund III
Footnotes to Schedule of Investments
August 31, 2006 (unaudited)

(A) Credit ratings are unaudited and are rated by Moody's Investors Service where Standard & Poor's ratings are not available.

(G) Security rated internally by John Hancock Advisers, LLC.

(S) This security is exempt from registration under Rule 144A of the Securities Act of 1933. Such security may be resold, normally to qualified institutional buyers, in transactions exempt from registration. Rule 144A securities amounted to $15,532,978 or 1.45% of the Fund's total investments as of August 31, 2006.

Parenthetical disclosure of a foreign country in the security description represents country of a foreign issuer.

The percentage shown for each investment category is the total value of that category as a percentage of the total investments of the Fund.

The cost of investments owned on August 31, 2006, including short-term investments, was $1,087,304,405. Gross unrealized appreciation and depreciation of investments aggregated $22,863,500 and $40,170,320, respectively, resulting in net unrealized depreciation of $17,306,820.

Footnotes to Schedule of Investments - Page 1


John Hancock         
Preferred Income Fund III       
Financial futures contracts         
August 31, 2006 (unaudited)         
 
  Number of       
Open contracts  contracts  Position  Expiration  Depreciation 

U.S. 10-Year Treasury Note  1,100  Short  December-06  ($506,132) 

Financial futures contracts


John Hancock         
Preferred Income Fund III     
Interest rate swap contracts       
August 31, 2006 (unaudited)       
 
  Rate type     

Notional  Payments made  Payments received  Termination  Appreciation 
amount  by Fund  by Fund  date   

$35,000,000  4.00% (a)  3-month LIBOR  Apr 09  $995,494 

 
(a) Fixed rate         

Interest rate swap contracts




ITEM 2. CONTROLS AND PROCEDURES.

(a) Based upon their evaluation of the registrant's disclosure controls and procedures as conducted within 90 days of the filing date of this Form N-Q, the registrant's principal executive officer and principal financial officer have concluded that those disclosure controls and procedures provide reasonable assurance that the material information required to be disclosed by the registrant on this report is recorded, processed, summarized and reported within the time periods specified in the Securities and Exchange Commission's rules and forms.

(b) There were no changes in the registrant's internal control over financial reporting that occurred during the registrant's last fiscal quarter that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting.

ITEM 3. EXHIBITS.

Separate certifications for the registrant's principal executive officer and principal financial officer, as required by Rule 30a-2(a) under the Investment Company Act of 1940, are attached.


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

John Hancock Preferred Income Fund III

By: /s/ Keith F. Hartstein
-------------------------------------
Keith F. Hartstein
President and Chief Executive Officer

Date: October 27, 2006

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By: /s/ Keith F. Hartstein
-------------------------------------
Keith F. Hartstein
President and Chief Executive Officer

Date: October 27, 2006

By: /s/ John G. Vrysen
-------------------------------------
John G. Vrysen

Executive Vice President and Chief Financial Officer

Date: October 27, 2006