The UB3LYP/EPR-II, UPBE0/EPR-II and UBP86/EPR-II DFT methods have been applied to study the protic and aprotic solvent effect on the g-tensor and molecular properties of o-semiquinone radicals. The solvent effect has been taken into account in two ways: by employing continuum dielectric approach and by explicit solvent molecules inclusion. Choice of the investigated systems has allowed to determinate the influence of increased aromaticity and the presence of heteroatoms on the radical properties. To reach the best efficiency of the theoretical studies the calculated Delta g(iso) values have been compared with these experimentally observed. (C) 2010 Elsevier B. V. All rights reserved.