Electrochemical copolymerization of aniline and p-phenylenediamine (PPD), and of N-(3-sulfopropyl)aniline (NSPA) and PPD, was performed by a potential cycling procedure. Acceleration of electropolymerization was found to proceed at a particular molar ratio of aniline and PPD. Electrocatalysis of the hydroquinone/benzoquinone (HQ/BQ) redox couple was shown to occur at electrodes covered with a film of copolymers of both types. At electrodes covered with the copolymer of aniline and PPD, a peak separation value as low as 0.035-0.045 V was found to be achievable for the studied redox couple by optimizing the electropolymerization conditions. Electrodes covered with the copolymer of NSPA and PPD show less efficient electrocatalysis.