The rate and mechanism of cadmium(II) electroreduction from electrolytes containing ε-caprolactam were found to significantly depend on the metal-to-additive ratio. Whatever the anion nature, the process sharply accelerates in the presence of an excess of cadmium cations, which form activated surface complexes with adsorbed ε-caprolactam molecules as bridging ligands. With an excess of the additive, metal depolarization due to the Ψ"-effect still persists in perchlorate media; in iodide solutions, ε-caprolactam inhibits this process. The formation of a dense adsorbed film composed of ε-caprolactam molecules and I– anions at the electrode ensures a high throwing power of the electrolyte and makes it possible to obtain uniform elastic organocadmium plating.