PROSPECTUS SUPPLEMENT
(To Prospectus Dated January 28, 1998)

                               OMNICOM GROUP INC.
                         219,205 Shares of Common Stock
                                ($.15 Par Value)

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      This document  supplements the Prospectus  dated January 28, 1998 relating
to 219,205 shares of Common Stock, par value $.15 per share (the "Common Stock")
of the Omnicom Group Inc., a New York corporation  ("Omnicom" or the "Company").
Each  share of Common  Stock  offered  hereby  was issued  upon  exchange  of an
Exchangeable  Share (an "Exchangeable  Share") of Omnicom Canada Inc. ("OCI"), a
corporation  incorporated  under  the laws of  Ontario,  originally  issued in a
private  offering in Canada by Palmer Jarvis Inc. (now amalgamated into OCI) and
the Company.  The shares of Common Stock offered hereby were initially  acquired
upon exchange of the Exchangeable  Shares in a private offering in Canada.  This
Prospectus Supplement is incorporated by reference into the Prospectus,  and all
terms used herein shall have the meaning assigned to them in the Prospectus.  On
October 1, 2002 the  closing  price of the Common  Stock as  reported on the New
York Stock  Exchange was $56.70 per share.  The Common Stock is traded under the
symbol "OMC."

      None of the Selling  Shareholders owns in excess of 1% of the Common Stock
of the Company and since the Selling  Shareholders may sell all, some or none of
the  shares of Common  Stock  offered  hereby,  no  estimate  can be made of the
aggregate  number of shares of Common  Stock that will be owned by each  Selling
Shareholder upon completion of the offering to which this Prospectus  Supplement
relates.  In accordance  with the Section of the  Prospectus  entitled  "Selling
Shareholders"  (which  appears  on page  10 of the  Prospectus),  the  following
information  is provided  with  respect to the  beneficial  owners of the Common
Stock:

                                           Amount of Shares         Amount of
                                          Beneficially Owned      Shares to be
Name of Selling Shareholder(s)           as of October 1, 2002  Offered for Sale
- ------------------------------           ---------------------  ----------------
Kathreen Ann Shapka                               55                   55

      Except for the  purchase  of the shares of Common  Stock and his  position
with OCI, the Selling  Shareholder has not had a material  relationship with the
Company or any of its affiliates within the past three years.

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      THESE  SECURITIES  HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES
AND EXCHANGE  COMMISSION OR ANY STATE SECURITY COMMISSION NOR HAS THE SECURITIES
AND  EXCHANGE  COMMISSION  OR ANY STATE  SECURITIES  COMMISSION  PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

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           The date of this Prospectus Supplement is October 4, 2002.