Comparative analysis of the ratio of the isomeric monomethyl ethers of 1-arylcyclohexane-1, 2-diols formed in the gas-phase and solvalytic acid-induced methanolysis of several 1- arylcyclohexene oxides indicates the intrinsic electronic factors determining the regio-and stereochemical course of the nucleophilic attack, related to the partial degree of carbocationic character at the reaction centre in the substitution transition state.