Data on cathodic processes in sulphate solutions containing Cu(II) and Sn(II) ions and H2SO4 with and without Laprol 2402C (OA) is given. The sequence of cathodic processes and their dependence on the electrolyte composition were determined. The presence of OA extended the range of cathodic current densities (i(c)) at which a high quality alloy was obtained. Electrolysis conditions under which the cathodic process rates considerably decrease were found. This is caused by passivation of the cathode surface by the film formed. The cathode passivation is accompanied by periodic oscillations. Anodic current peaks, i.e. ’reverse’ maxima, were found to occur during reverse potential sweeps. The peak values depended on the potential at which the reverse sweep began.