POWER OF ATTORNEY







KNOW ALL BY THESE PRESENTS, THAT THE UNDERSIGNED HEREBY CONSTITUTES AND APPOINTS





EACH OF JILL GEISENHEIMER, SOFIA ROSALA AND N. JEFFREY KLAUDER SIGNING SINGLY,





THE UNDERSIGNED'S TRUE AND LAWFUL ATTORNEY-IN-FACT TO:







(1) execute for and on behalf of the undersigned, in the undersigned's capacity



as an officer and/or director of SEI Investment Company (the "Company"),



Forms 3, 4, and 5 in accordance with Section 16(a) of the Securities



Exchange Act of 1934 and the rules thereunder;





(2) do and perform any and all acts for and on behalf of the undersigned which



may be necessary or desirable to complete and execute any such Form 3, 4 or



5 and and timely file such form with the United States Securities and



Exchange Commission and any stock exchange or other similar authority; and







(3) take any other action of any type whatsoever in connection with the



foregoing which, in the opinion of such attorney-in-fact, may be of benefit to,



in the best interest of, or legally required by, the undersigned, it being



understood that the documents executed by such attorney-in-fact on



behalf of the undersigned pursuant to this Power of Attorney shall be in such



form and shall contain such terms and conditions as such attorney-in-fact may



approve in such attorney-in-fact's discretion.







The undersigned hereby grants to each such attorney-in-fact full power and



authority to do and perform any and every act and thing whatsoever requisite,



necessary, or proper to be done in the exercise of any of the rights and powers



herein granted, as fully to all intents and purposes as the undersigned



might or could do if personally present, with full power of substitution or



revocation, hereby ratifying and confirming all that such attorney-in-fact, or



such attorney-in-fact's substitute or substitutes, shall lawfully do or cause to



be done by virtue of this power of attorney and the rights and powers herein



granted.  The undersigned acknowledges that the foregoing attorneys-in-fact,



in serving in such capacity at the request of the undersigned, are not assuming,



nor is the Company assuming, any of the undersigned's responsibilities to comply



with Section 16 of the Securities Exchange Act of 1934.







This Power of Attorney shall remain in full force and effect until the



undersigned is no longer required to file Forms 3, 4, and 5 with respect to the



undersigned's holdings of and transactions in securities issued by the Company,



unless earlier revoked by the undersigned in a signed writing delivered to the



foregoing attorneys-in-fact.







IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be



executed as of this 20 day of July, 2004.



                                                       /S/ Carl A. Guarino

                                                       Signature



                                                       Carl A. Guarino

                                                       Print Name