The effect of silicotungstic acid (STA) on the electrodeposition of copper in sulphuric acid was investigated. It was shown that the effect of STA on the kinetic parameters of electrodeposition depends on the electrodeposition overpotential. In particular, the effect of STA on the potential region where the reversible electrodeposition occurred was determined. The variation of the electrodeposition efficiency with the electrodeposition overpotential was deduced. These various results are correlated to the chemical composition of the electrodeposits.