The Gaussian-2 theory (G2) and its modified versions (G2MP2, G2M(CCS), and G2M(CC6)) were applied to predict electron properties such as electron affinity and thermochemistry properties such as atomization energy, enthalpy of formation, and the bond dissociation energies of the PFn/PFn- series. The atomization energies, enthalpies of formation, bond dissociation energies, and adiabatic electron affinities of the PFn/PFn- series calculated according to the G2 theory and its modified versions are congruous with the available experimental data. Among the four tested G2 versions, the G2M(CC5) method is the most reliable for all of the calculated properties. It underestimates the Delta(f)H degrees of PF3 and PF5 by about 4 kcal/mol and the EA of P and PF by 0.19 and 0.05 eV. G2M(CC5) has less error accumulation than the G2 theory. Moreover, fewer computational demands makes the G2M(CC5) theory more suitable for larger system than the G2 method. This study also reveals that all bond dissociation energies of PFn-1-F- predicted by the BHLYP/DZP++ approach are quite close to those predicted by the G2 theory and its modifications with a difference of approximately 2 kcal/mol. However, the BHLYP/DZP++ method seriously underestimates the PFn-1-F and PFn-1-F bond dissociation energies (by 10-20 kcal/mol).