Abstract A detailed quantum chemical study was performed at the BMC-CCSD//B3LYP/6-311G(d,p) level to explore the mechanism of the O( 1D) + CH 3OCF 3 reaction. Three feasible initial association intermediates ( a, b, and c) and six energetically allowed paths are located. Our calculations show that the primary products are P 2 and P 3 , while P 1 , P 4 , and P 6 are less competitive. Due to the low-lying intermediates and transition states involved in the dominant paths, the reaction is expected to occur rapidly, which is consistent with the experimental measurement. The present theoretical studies may provide useful information on the issues of the reaction mechanism and product distributions.