PPy/CdS composite films made from polypyrrole (PPy) with embedded semiconductor (CdS) quantum dots were obtained by electropolymerization of pyrrole in the presence the CdS nanoparticles dispersed in the electrolytic aqueous solution. For the characterization of the modified surface electrode by PPy-CdS, the scan electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV-visible were used. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) have been used to investigate the electrochemical behaviour of the resulting materials. The illumination effects are also observed in the reduced form of the polymer. This study showed that the presence of CdS nanoparticles in the polypyrrole film improves the optical properties of PPy via a simple preparation method and show that these films have potential in the photoelectrochemical applications such as photovoltaic cells. (C) 2010 Elsevier B.V. All rights reserved.