The mixed adsorption layers of tetramethylthiourea and a neutral detergent formed at the electrode surface in 1 M NaClO4 are described in this paper. The systems were characterized by the measurement of differential capacity, zero charge potential, and surface tension at the same potential. The data were analyzed to obtain the surface pressure and relative surface excess of tetramethylthiourea as a function of electrode charge and bulk concentration of the studied compounds. The values of the lateral interaction parameters, obtained in the presence and in the absence of decanoyl-N-methylglucamide (C17H35NO6), change differently depending on the isotherm used, but Delta G degrees values were clearly smaller in the presence of C17H35NO6. Electrostatic parameters of the inner layer were assigned. A compensation for the inhibition and accelerating effect was obtained for the bulk concentrations ratio c(TMTU) : c(detergent) approximate to 13.3. For c(TMTU) > 0.01 M the acceleration of Zn2+ electroreduction appeared.