Hydrogen abstractions by O(P-3) from a set of fluorinated methanes, CFnH4-n+O(P-3) --> CFnH4-n... O --> .CFnH3-n + .OH (n = 0,1,2), were studied using ab initio methods. Geometries of the reactants and transition states were optimized at the UMP2/6-311G** level of theory, and activation energies were calculated using a modified GAUSSIAN 2 ((G) over cap (2)) theory. The potential-energy curves for the transition states were computed in order to obtain the transmission coefficients, kappa, for the reactions studied. We found that kappa (aver) = 1.12 +/- 0.01. Activation energies, activation enthalpies and rate constants were computed. Good agreement, (the average difference is 0.9 +/- 0.4 kcal/mol for the present study), was found between the ab initio activation energies, DeltaG(theor.)double dagger, and the experimental activation energies, DeltaG(expt'l)double dagger.