The retention behaviour of some phenols and aromatic amines on CN and Diol precoated high-performance thin-layer chromatographic plates was examined using normal-phase eluent systems: polar modifier (2-propanol, ethyl acetate, ethyl methyl ketone, dioxane, tetrahydrofuran or diisopropyl ether) in n-heptane. The results were compared with the retention parameters of investigated compounds obtained in the same eluent systems on bare silica. The results are presented by the comparison of δRMvalues for pairs of positional isomers and by the RM Ivs. RM IIrelationships of phenols and anilines for CN-silica - silica, diol-silica - silica and CN - diol stationary phases.