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                                                                      Exhibit 24


                                POWER OF ATTORNEY

      The undersigned director of OM Group, Inc. (the "Company"), a Delaware
corporation, which anticipates filing with the Securities and Exchange
Commission, Washington, D.C., under the provisions of the Securities Exchange
Act of 1934, as amended, an Annual Report on Form 10-K for the Company's fiscal
year ended December 31, 2005, hereby constitutes and appoints JOSEPH M.
SCAMINACE, with full power of substitution and resubstitution, as attorney to
sign for the undersigned and in his or her name, place and stead, as director of
said Company, said Annual Report and any and all amendments and exhibits
thereto, and any and all applications and documents to be filed with the
Securities and Exchange Commission pertaining to such Annual Report, with full
power and authority to do and perform any and all acts and things whatsoever
requisite, necessary or advisable to be done in the premises, as fully and for
all intents and purposes as the undersigned could do if personally present,
hereby approving the acts of said attorney and any such substitute.

      IN WITNESS WHEREOF, this Power of Attorney has been signed this 5th day of
March, 2006.


                                                  /s/ Richard W. Blackburn
                                                  ------------------------------
                                                  Richard W. Blackburn
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                                POWER OF ATTORNEY

      The undersigned director of OM Group, Inc. (the "Company"), a Delaware
corporation, which anticipates filing with the Securities and Exchange
Commission, Washington, D.C., under the provisions of the Securities Exchange
Act of 1934, as amended, an Annual Report on Form 10-K for the Company's fiscal
year ended December 31, 2005, hereby constitutes and appoints JOSEPH M.
SCAMINACE, with full power of substitution and resubstitution, as attorney to
sign for the undersigned and in his or her name, place and stead, as director of
said Company, said Annual Report and any and all amendments and exhibits
thereto, and any and all applications and documents to be filed with the
Securities and Exchange Commission pertaining to such Annual Report, with full
power and authority to do and perform any and all acts and things whatsoever
requisite, necessary or advisable to be done in the premises, as fully and for
all intents and purposes as the undersigned could do if personally present,
hereby approving the acts of said attorney and any such substitute.

      IN WITNESS WHEREOF, this Power of Attorney has been signed this 3rd day of
March, 2006.

                                                  /s/ Steven J. Demetriou
                                                  ------------------------------
                                                  Steven J. Demetriou
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                                POWER OF ATTORNEY

      The undersigned director of OM Group, Inc. (the "Company"), a Delaware
corporation, which anticipates filing with the Securities and Exchange
Commission, Washington, D.C., under the provisions of the Securities Exchange
Act of 1934, as amended, an Annual Report on Form 10-K for the Company's fiscal
year ended December 31, 2005, hereby constitutes and appoints JOSEPH M.
SCAMINACE, with full power of substitution and resubstitution, as attorney to
sign for the undersigned and in his or her name, place and stead, as director of
said Company, said Annual Report and any and all amendments and exhibits
thereto, and any and all applications and documents to be filed with the
Securities and Exchange Commission pertaining to such Annual Report, with full
power and authority to do and perform any and all acts and things whatsoever
requisite, necessary or advisable to be done in the premises, as fully and for
all intents and purposes as the undersigned could do if personally present,
hereby approving the acts of said attorney and any such substitute.

      IN WITNESS WHEREOF, this Power of Attorney has been signed this 2nd day of
March, 2006.


                                                  /s/ Katharine L. Plourde
                                                  ------------------------------
                                                  Katharine L. Plourde
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                                POWER OF ATTORNEY

      The undersigned director of OM Group, Inc. (the "Company"), a Delaware
corporation, which anticipates filing with the Securities and Exchange
Commission, Washington, D.C., under the provisions of the Securities Exchange
Act of 1934, as amended, an Annual Report on Form 10-K for the Company's fiscal
year ended December 31, 2005, hereby constitutes and appoints JOSEPH M.
SCAMINACE, with full power of substitution and resubstitution, as attorney to
sign for the undersigned and in his or her name, place and stead, as director of
said Company, said Annual Report and any and all amendments and exhibits
thereto, and any and all applications and documents to be filed with the
Securities and Exchange Commission pertaining to such Annual Report, with full
power and authority to do and perform any and all acts and things whatsoever
requisite, necessary or advisable to be done in the premises, as fully and for
all intents and purposes as the undersigned could do if personally present,
hereby approving the acts of said attorney and any such substitute.

      IN WITNESS WHEREOF, this Power of Attorney has been signed this 6th day of
March, 2006.


                                                  /s/ William J. Reidy
                                                  ------------------------------
                                                  William J. Reidy