Changes in geometry of NO and N(Me-2) functional groups under the impact of substituents have been investigated. In the series of p-substituted nitrosobenzenes, and in the series of p-substituted N, N-dimethylanilines the geometric parameters of the groups were regressed against Hammett constants, charges of the substituent active region, qSAR(X), and charges of the analogous region comprising the NO group, qSAR(NO) or the N(Me-2) group, qSAR(NMe2). An accurate correspondence was found between the geometric characteristics of the groups and electronic properties of substituents, qualified as qSAR(X). The correspondence was even better when the charge of the region comprising the functional group, qSAR(NO) or qSAR(NMe2) instead of qSAR(X), was considered. (C) 2009 Elsevier B. V. All rights reserved.