A set of 7 Benson group additive values (GAV) together with 15 correction terms for non-nearest neighbor interactions (NNI) is developed to calculate the gas phase standard enthalpies of formation, entropies and heat capacities of monocyclic aromatic compounds containing methyl, ethyl, vinyl, formyl, hydroxyl, and methoxy substituents. These GAVs are obtained through least squares regression of a database of thermodynamic properties of 143 molecules, calculated at the post-Hartree-Fock G4 composite method. Out of the 15 NNIs, which account for several well-known substituent effects in aromatic molecules, 13 have been determined for the first time. All but two group additively calculated standard enthalpies of formation agree within 4 kJ mol(-1). The entropies and the heat capacities generally deviate less than 4 J mol(-1) K-1 from the ab initio results. Natural bond orbital analysis is utilized to identify the underlying causes of the observed NNIs. (c) 2015 American Institute of Chemical Engineers