Coulombic or cathode efficiencies (CE) were determined for the reverse pulse plating of copper from CuSO₄/H₂SO₄ electrolyte for a variety of pulse conditions. The CE was seen to decrease as the magnitude of the current on the anodic pulse increased. This may be explained by an increase in Cu⁺ intermediates near the electrode surface and was verified by polarization data obtained from a rotating ring disc electrode (RRDE). The influence of certain additives on the CE during reverse pulse plating and on the polarization curves was also examined. When polyethylene glycol and Cl^– (0.86mm) were added to the electrolyte, the CE was observed to drop significantly for a particular set of pulse parameters. The polarization curves at the RRDE suggested that the copper-electrolyte interface was blocked by an adsorbed layer over a wide potential range. The results are explained in terms of a model in which Cl^– ions are concentrated near the electrode surface within the adsorbed polyethylene glycol layer and this is supported by observed rotational dependencies for the RRDE.