Exhibit 23

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration Statements on Forms S-8 (Nos. 333-19103 and 333-19099) of Cabot Corporation of our report dated June 23, 2006 relating to the financial statements of the Cabot Retirement Savings Plan, which appears in this Form 11-K.

/s/ PricewaterhouseCoopers LLP

Boston, Massachusetts
June 23, 2006