**Exhibit 24**POWER OF ATTORNEY     The undersigned director of OM Group, Inc. (the “Company”), a Delaware corporation, whichanticipates filing with the Securities and Exchange Commission, Washington, D.C., under theprovisions of the Securities Exchange Act of 1934, as amended, an Annual Report on Form 10-K forthe Company’s fiscal year ended December 31, 2006, hereby constitutes and appoints JOSEPH M.SCAMINACE and KENNETH HABER, with full power of substitution and resubstitution, as attorney tosign for the undersigned and in his or her name, place and stead, as director of said Company, saidAnnual Report and any and all amendments and exhibits thereto, and any and all applications anddocuments 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 theundersigned could do if personally present, hereby approving the acts of said attorney and any suchsubstitute.     IN WITNESS WHEREOF, this Power of Attorney has been signed this 22 day of February, 2007.                          /s/ Richard W. Blackburn   Richard W. Blackburn     
 

 
     POWER OF ATTORNEY     The undersigned director of OM Group, Inc. (the “Company”), a Delaware corporation, whichanticipates filing with the Securities and Exchange Commission, Washington, D.C., under theprovisions of the Securities Exchange Act of 1934, as amended, an Annual Report on Form 10-K forthe Company’s fiscal year ended December 31, 2006, hereby constitutes and appoints JOSEPH M.SCAMINACE and KENNETH HABER, with full power of substitution and resubstitution, as attorney tosign for the undersigned and in his or her name, place and stead, as director of said Company, saidAnnual Report and any and all amendments and exhibits thereto, and any and all applications anddocuments 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 theundersigned could do if personally present, hereby approving the acts of said attorney and any suchsubstitute.     INWITNESS WHEREOF, this Power of Attorney has been signed this23 day of February, 2007.                     /s/ David L. Pugh   David L. Pugh     
 

 
     POWER OF ATTORNEY     The undersigned director of OM Group, Inc. (the “Company”), a Delaware corporation, whichanticipates filing with the Securities and Exchange Commission, Washington, D.C., under theprovisions of the Securities Exchange Act of 1934, as amended, an Annual Report on Form 10-K forthe Company’s fiscal year ended December 31, 2006, hereby constitutes and appoints JOSEPH M.SCAMINACE and KENNETH HABER, with full power of substitution and resubstitution, as attorney tosign for the undersigned and in his or her name, place and stead, as director of said Company, saidAnnual Report and any and all amendments and exhibits thereto, and any and all applications anddocuments 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 theundersigned could do if personally present, hereby approving the acts of said attorney and any suchsubstitute.     IN WITNESS WHEREOF, this Power of Attorney has been signed this 19th day of February, 2007.                     /s/ Gordon A. Ulsh   Gordon A. Ulsh     
 

 
     POWER OF ATTORNEY     The undersigned director of OM Group, Inc. (the “Company”), a Delaware corporation, whichanticipates filing with the Securities and Exchange Commission, Washington, D.C., under theprovisions of the Securities Exchange Act of 1934, as amended, an Annual Report on Form 10-K forthe Company’s fiscal year ended December 31, 2006, hereby constitutes and appoints JOSEPH M.SCAMINACE and KENNETH HABER, with full power of substitution and resubstitution, as attorney tosign for the undersigned and in his or her name, place and stead, as director of said Company, saidAnnual Report and any and all amendments and exhibits thereto, and any and all applications anddocuments 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 theundersigned could do if personally present, hereby approving the acts of said attorney and any suchsubstitute.     INWITNESS WHEREOF, this Power of Attorney has been signed this23 day of February, 2007.                     /s/ Steven J. Demetriou   Steven J. Demetriou     
 

 
     POWER OF ATTORNEY     The undersigned director of OM Group, Inc. (the “Company”), a Delaware corporation, whichanticipates filing with the Securities and Exchange Commission, Washington, D.C., under theprovisions of the Securities Exchange Act of 1934, as amended, an Annual Report on Form 10-K forthe Company’s fiscal year ended December 31, 2006, hereby constitutes and appoints JOSEPH M.SCAMINACE and KENNETH HABER, with full power of substitution and resubstitution, as attorney tosign for the undersigned and in his or her name, place and stead, as director of said Company, saidAnnual Report and any and all amendments and exhibits thereto, and any and all applications anddocuments 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 theundersigned could do if personally present, hereby approving the acts of said attorney and any suchsubstitute.     IN WITNESS WHEREOF, this Power of Attorney has been signed this 21 day of February, 2007.                     /s/ Katharine L. Plourde   Katharine L. Plourde     
 

 
     POWER OF ATTORNEY     The undersigned director of OM Group, Inc. (the “Company”), a Delaware corporation, whichanticipates filing with the Securities and Exchange Commission, Washington, D.C., under theprovisions of the Securities Exchange Act of 1934, as amended, an Annual Report on Form 10-K forthe Company’s fiscal year ended December 31, 2006, hereby constitutes and appoints JOSEPH M.SCAMINACE and KENNETH HABER, with full power of substitution and resubstitution, as attorney tosign for the undersigned and in his or her name, place and stead, as director of said Company, saidAnnual Report and any and all amendments and exhibits thereto, and any and all applications anddocuments 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 theundersigned could do if personally present, hereby approving the acts of said attorney and any suchsubstitute.     IN WITNESS WHEREOF, this Power of Attorney has been signed this 23rd day of February, 2007.         /s/ William J. Reidy   William J. Reidy