Abstract. The two-step reduction of Zn 2+ ions at the dropping mercury electrode in 2, 3, and 4 mol dmNaClO4 with the addition of tert-butanol, using the impedance method in wide potential and frequency ranges was examined. An inhibiting influence of tert-butanol is shown in the used experimental systems, which increases with the rise of the base electrolytes concentration. This effect caused by NaClO4 concentration change is probably linked with the electrodes surface and the Zn + aquaion composition change. (doi: 10.5562/cca1726)