UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

                                  SCHEDULE 13G

                   UNDER THE SECURITIES EXCHANGE ACT OF 1934


                        CORPORATE OFFICE PROPERTIES TRUST
--------------------------------------------------------------------------------
                                (NAME OF ISSUER)


                                  COMMON SHARES
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                         (TITLE OF CLASS OF SECURITIES)


                                    22002T108
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                                 (CUSIP NUMBER)


                                DECEMBER 31, 2004
--------------------------------------------------------------------------------
                          (DATE OF EVENT WHICH REQUIRES
                            FILING OF THIS STATEMENT)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

[_]      Rule 13d-1(b)
[X]      Rule 13d-1(c)
[_]      Rule 13d-1(d)




CUSIP NO. 22002T108                  13G                       PAGE 2 OF 6 PAGES

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   1      NAME OF REPORTING PERSONS
          S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS

          ING Groep N.V.
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   2      CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
                                                                         (a) [_]
          Not Applicable                                                 (b) [_]
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   3      SEC USE ONLY


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   4      CITIZENSHIP OR PLACE OF ORGANIZATION

          The Netherlands
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                       5   SOLE VOTING POWER
                           
                           1,963,200(1)
     NUMBER OF         ---------------------------------------------------------
       SHARES          6   SHARED VOTING POWER
    BENEFICIALLY           
    OWNED BY EACH          0
      REPORTING        ---------------------------------------------------------
    PERSON WITH:       7   SOLE DISPOSITIVE POWER
                           
                           1,963,200(1)
                       ---------------------------------------------------------
                       8   SHARED DISPOSITIVE POWER
                           
                           0
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   9      AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          1,963,200
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   10     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES
          CERTAIN SHARES                                                   [_]

          Not Applicable
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   11     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

          5.3%(2)
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   12     TYPE OF REPORTING PERSON

          HC
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----------

1    These shares are held by indirect subsidiaries of ING Groep N.V. in their
     role as a discretionary manager of client portfolios.
2    As of November 2, 2004, 36,801,533 common shares were issued and 
     outstanding. Source:  Issuer's Form 10-Q for the quarter ended September
     30, 2004.



                                      -2-



ITEM 1(A).    NAME OF ISSUER:

              Corporate Office Properties Trust

ITEM 1(B).    ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:

              8815 Centre Park Drive
              Suite 400
              Columbia, MD 21045

ITEM 2(A).    NAME OF PERSON FILING:

              ING Groep N.V.

ITEM 2(B).    ADDRESS OF PRINCIPAL BUSINESS OFFICE OR, IF NONE, RESIDENCE:

              Amstelveenseweg 500
              1081 KL Amsterdam
              P.O. Box 810
              1000 AV Amsterdam
              The Netherlands

ITEM 2(C).    CITIZENSHIP:

              See item 4 on Page 2

ITEM 2(D).    TITLE OF CLASS OF SECURITIES:

              Common Shares

ITEM 2(E).    CUSIP NUMBER:

              22002T108

ITEM 3.       IF THIS STATEMENT IS FILED PURSUANT TO RULES 13D-1(B), OR
              13D-2(B) OR (C), CHECK WHETHER THE PERSON FILING IS A:  
              (Not Applicable)

     (a) |_|  Broker or dealer registered under Section 15 of the Securities 
              Exchange Act of 1934, as amended (the "Exchange Act");

     (b) |_|  Bank as defined in Section 3(a)(6) of the Exchange Act;

     (c) |_|  Insurance company as defined in Section 3(a)(19) of the Exchange
              Act;



                                      -3-



     (d) |_|   Investment company registered under Section 8 of the Investment
               Company Act of 1940, as amended (the "Investment Company Act");

     (e) |_|   Investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E) 
               under the Exchange Act;

     (f) |_|   Employee benefit plan or endowment fund in accordance with 
               Rule 13d-1(b)(1)(ii)(F) under the Exchange Act;

     (g) |_|   Parent holding company or control person in accordance with 
               Rule 13d-1(b)(ii)(G) under the Exchange Act;

     (h) |_|   Savings association as defined in Section 3(b) of the Federal 
               Deposit Insurance Act;

     (i) |_|   Church plan that is excluded from the definition of an 
               investment company under Section 3(c)(14) of the Investment 
               Company Act;

     (j) |_|   Group in accordance with Rule 13d-1(b)(1)(ii)(J) under the 
               Exchange Act.

ITEM 4.        OWNERSHIP.

     (a)       Amount beneficially owned:

                      See item 9 on Page 2

     (b)       Percent of class:

                      See item 11 on Page 2

     (c)       Number of shares as to which such person has:

               (i)    Sole power to vote or to direct the vote:

                      See item 5 on Page 2

               (ii)   Shared power to vote or to direct the vote:

                      See item 6 on Page 2

               (iii)  Sole power to dispose or to direct the disposition of:

                      See item 7 on Page 2


                                      -4-


               (iv)   Shared power to dispose or to direct the disposition of:

                      See item 8 on Page 2

ITEM 5.        OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS.

               Not Applicable

ITEM 6.        OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON.

               Not Applicable

ITEM 7.        IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH 
               ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING 
               COMPANY OR CONTROL PERSON.

               Not Applicable

ITEM 8.        IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP.

               Not Applicable

ITEM 9.        NOTICE OF DISSOLUTION OF GROUP.

               Not Applicable

ITEM 10.       CERTIFICATION.

               By signing below we certify that, to the best of our knowledge
               and belief, the securities referred to above were not acquired
               and are not held for the purpose of or with the effect of
               changing or influencing the control of the issuer of the
               securities and were not acquired and are not held in connection
               with or as a participant in any transaction having that purpose
               or effect.


                                      -5-



                                    SIGNATURE


         After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.


                                             February 4, 2005
                                             -----------------------------------
                                             (Date)


                                             ING GROEP N.V.


                                             By:

                                             /s/ Cornelis Blokbergen
                                             -----------------------------------
                                             (Signature)


                                             Cornelis Blokbergen
                                             Head Legal Department
                                             -----------------------------------
                                             (Name/Title)


                                             /s/ Huib D. ter Haar
                                             -----------------------------------
                                             (Signature)


                                             Huib D. ter Haar
                                             Group Compliance Officer
                                             -----------------------------------
                                             (Name/Title)