Cabot (CBT) 10-Q 2008 Q3 Quarterly report

EXHIBIT 32

Certifications Pursuant to 18 U.S.C. Section 1350,

as Adopted Pursuant to Section 906 of the

Sarbanes-Oxley Act of 2002

In connection with the filing of the Quarterly Report on Form 10-Q for the quarter ended June 30, 2008 (the “Report”) by Cabot Corporation (the “Company”), each of the undersigned hereby certifies pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that, to his knowledge:

1. The Report fully complies with the requirements of section 13 (a) or 15 (d) of the Securities Exchange Act of 1934, as amended; and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ PATRICK M. PREVOST

Patrick M. Prevost

President and Chief Executive Officer

August 8, 2008

/s/ JONATHAN P. MASON

Jonathan P. Mason

Executive Vice President and

Chief Financial Officer

August 8, 2008