The proper deposition bath composition for electrochemical synthesis of the CdSe deposit in the hexagonal structure of the right elemental stoichiometry and photoreacting as an n-type semiconductor which can be used as a stable photoanode is investigated The deposits were prepared by a cyclic potentiodynamic technique and the concentration of Cd2+ and SeO32- in the deposition baths varied from 10(-4) M to 0 1 M and from 10(-5) M to 10(-3) M respectively The electrochemical the X-ray diffraction (EDS and XRD) and the photoactivity studies of a number of deposits have shown that application of the solution composition following Cd Se = 5 1 results in deposition of the stoichiometric CdSe The detected ratio of reagents is explained on the base of reaction mechanism and necessary excess of cadmium ions preventing CdSe deposit dissolution The procedure of CdSe electrosynthesis was developed to yield of a direct semiconductor in the hexagonal structure The necessity for cadmium cations excess is explained on the basis of the mixed electrochemical/chemical deposition mechanism (C) 2010 Published by Elsevier Ltd