When dealing with organic peroxides in both laboratory and industrial applications, the relative strengths of the O-O bond are of vital importance, both from a safety and mechanistic perspective. Although it is well known that such oxidizing agents are highly reactive, reliable O-O bond dissociation energies (BDEs) have only recently been established. In an earlier report, we suggested a median O-O BDE value of ca. 45 kcal/mol for a variety of well-known peroxides based upon G2 ab initio calculations. In the present report, we have calculated the O-O BDE of twenty peroxides of varying structures at a more accurate CBS-APNO level. We have also compared these bond energies to the corresponding BDEs calculated with several DFT functionals and shown that the M06-2X functional produces O-O bond energies that compare very favorably with G4 and CBS-APNO values.