The variation in selectivity of aromatic hydrocarbons with bisubstituted polar groups is investigated in systems consisting of C18 stationary phase and ternary eluents. The solutions of the ternary eluents were obtained by mixing binary solvents (organic modifier + water) of similar eluent strength. Acetonitrile, methanol and tetrahydrofuran were the organic modifiers applied. The influence of the organic solvent type and its concentration in the ternary mobile phase on retention and selectivity of the solutes is discussed. An approach previously presented by our group was adapted to explain the selectivity changes.