POWER OF ATTORNEY



 Know all by these presents, that the undersigned hereby

constitutes and appoints each of Jane A. Bell, Michaela

Allbee and Brian A. Berube, 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 Cabot

Corporation (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, complete and execute

any amendment or amendments thereto, and timely file such

form with the United States Securities and Exchange

Commission and any stock exchange or 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.  The

undersigned hereby revokes any previous powers of attorney

delivered to the Company concerning the subject matter

hereof.



 IN WITNESS WHEREOF, the undersigned has caused this Power of

Attorney to be executed as of this 10th day of March, 2004.





/s/ Carol A. Flack

Signature











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