The synthesis of polycrystalline thin films of cubic zinc cadmium selenide by electrochemical plating on conducting substrates is described. The influence of deposition parameters, electrolyte composition and deposition potential on the crystallinity, composition, band gap and lattice constant of the films is discussed. The behaviour of zinc cadmium selenide thin films as an absorber material in a photoelectrochemical cell with polysulphide as electrolyte and as a window material in a CdTe photovoltaic cell is described.