Exhibit 24



                                POWER OF ATTORNEY



         KNOW ALL MEN BY THESE PRESENTS: That the undersigned has made,
constituted and appointed, and by this instrument does make, constitute and
appoint ROBERT PIERCE, ELIZABETH SHAUGHNESSY and CIPRIANO BEREDO, acting
individually, as his or her true and lawful attorney, for him or her, and in his
or her name, place and stead, to affix, as attorney-in-fact, the signature of
the undersigned to any reports or filings to the Securities and Exchange
Commission on or in connection with Forms 3, 4, 5 or 144 with respect to
transactions or holdings by the undersigned in equity securities issued by OM
Group, Inc., a Delaware corporation, and to any and all amendments to such
reports, giving and granting unto each such attorney-in-fact full power and
authority to do and perform every act and thing whatsoever necessary to be done
in the premises, as fully as the undersigned might or could do if personally
present, hereby ratifying and confirming all that each such attorney-in-fact
shall lawfully do or cause to be done by virtue hereof.

          This Power of Attorney shall expire on the date the undersigned is no
longer required to file Forms 3, 4, 5 or 144 reports with the Securities and
Exchange Commission with respect to holdings of and transactions in securities
issued by OM Group, Inc., unless revoked in writing prior thereto.

          IN WITNESS WHEREOF, this Power of Attorney has been signed at Key
Tower, Cleveland, Ohio, as of the 2nd day of May, 2006.




                                                  /s/ Stephen Dunmead
                                        ---------------------------------------
                                                     Stephen Dunmead