The thermodynamic properties of unsubstituted, mono‐, and di‐substituted toluene derivatives and benzylic radicals with hydroxy, methoxy, formyl, vinyl, methyl, and ethyl substituents are calculated with the bond additivity corrected (BAC) post‐Hartree‐Fock CBS‐QB3 method. Benson's group additivity (GA) scheme is extended to toluene derivatives by determining six group additive value (GAV) and five non‐nearest neighbor interaction (NNI) parameters through least‐squares regression to a database of thermodynamic properties of 168 compounds and to benzylic radicals by defining 6 GAV and 14 NNI parameters based on a set of 168 radicals. Comparison between CBS‐QB3/BAC and GA‐calculated thermodynamic values shows that the standard enthalpies of formation generally agree within 4 kJ mol⁻¹, whereas the entropies and the heat capacities generally deviate <4 J mol⁻¹ K⁻¹. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3649–3661, 2018