The specific adsorption of H2PO4- ions accompanying the upd of Zn2+ ions on platinum electrodes has been studied by a radiotracer technique using P-32 labelled phosphate species in the presence of a great excess of ClO4- ions. It has been found that the specific adsorption of species induced by Zn adatoms depends on pH and at a given potential on the concentration of Zn2+ ions.