In this paper we compare the structural, optical and photoelectrochemical properties of CdS, ZnS, and CdS:ZnS (50:50)W screen-printed and sintered polycrystalline films, with the properties of analogous nanostructured films elaborated by chemical deposition onto SnO2 modified substrates. Due to the characteristics of both deposition processes, the coupled polycrystalline system consisted of a heterogeneous film composed of a Cd-rich ternary compound, plus the remnant chalcogenide and oxide phases. However, the coupled nanostructured film was an homogeneous film composed primarily of a Zn-rich ternary compound with high crystallinity. The differences in composition and microstructure caused important differences in the optical and photoelectrochemical properties of these films. X-ray diffraction, optical spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy studies provided a tool to identify the contribution of different semiconductor phases, surface states and charge transport mechanisms.