Electrodeposited Ni-Mo-Cd composites are of considerable practical interest as electrocatalysts for the cathodic production of hydrogen gas in water electrolysers, and as cathode materials for chloralkali and chlorate cells where minimization of electric power consumption is of concern economically. The present work extends the study of the electrocatalytic behaviour of these materials and addresses the influence of cadmium content and the nature of the substrate on which the composites are deposited, particularly with regard to the behaviour and state of H species adsorbed during hydrogen evolution. In the case of a carbon-based, gas-diffusion type electrode substrate, the behaviour of the HER on electrodeposited Ni-Mo-Cd is significantly different from that of the same electrodeposit on a nickel substrate.