EXHIBIT 23

            CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We hereby consent to the incorporation by reference in the Registration
Statements on Form S-3 (No. 333-64787) and on Form S-8 (Nos. 333-03683,
333-19103, 333-19099, 333-82353, 333-96879 and 333-96881) of Cabot Corporation
of our report dated December 14, 2005 relating to the financial statements,
management's assessment of the effectiveness of internal control over financial
reporting and the effectiveness of internal control over financial reporting,
which appears in this Form 10-K.

/s/ PricewaterhouseCoopers LLP
Boston, Massachusetts
December 14, 2005