N,N- and 2,6-disubstituted anilines were oxidized by cerium(IV) perchlorate in aqueous solutions of perchloric acid to the corresponding derivatives of 4,4′-diphenoquinonediimine and N-phenyl-p-phenylenediimine in high yields. The type of the products obtained was determined by the properties of the substituents, by steric hindrance, and by the concentration of protons in the reaction mixtures. On the basis of experimental data and quantum mechanical calculations, which were performed using the semi-empirical AM1 method, a reaction mechanism was suggested.