Theoretical studies for CF3X- (X=Cl,Br,I) anions and its parent molecules are presented. Equilibrium structures of molecular anions were found to be significantly different from those of the neutral molecules since the electron attachment elongates the C-X bond. The complete basis set extrapolation method for the Moller-Plesset second-order perturbation theory has been applied for computing vertical and adiabatic molecular electron affinities, dissociation energies of anions, and neutral molecules, and the enthalpies of dissociative electron attachment reactions.