Adsorption of the mixture of thiourea-polyethylene glycols of molecular weights 400 and 10000 on a mercury electrode in 1M NaClO4 was described. The experimental data were obtained from the measurements of differential capacity and kinetic parameters of Zn(II) ion reduction as a piloting ion. It was stated that the Zn(II) ions reduction could be accelerated, inhibited or the effect of compensation of these phenomena could take place depending on the ratio of molar concentrations of the studied substances. The adsorption parameters of thiourea in the presence of various concentrations of polyethylene glycols as well as electrostatic parameters of the internal layer were given.