An electrophoretic deposition (EPD) procedure was adopted for the cathodic preparation of thin films of conducting polymer/metal oxide nanocomposites with a core-shell structure. The deposition process was investigated at different potentials and in various solvents. The mechanism and kinetics of the electrophoretic deposition were studied via quartz crystal microbalance (QCM) and zeta-potential measurements. The properties of the composite layers were studied by electrochemical methods (cyclic voltammetry, impedance spectroscopy) and photocurrent measurements. The reversible redox potential of polythiophene films was about 0.75 V-SCE. The p-type semiconducting behaviour of the reduced polythiophene was studied by photocurrent measurements. In the case of using TiO2 (n-type semiconductor) as a core material, an n/p heterojunction was observed. In the photocurrent spectra the maximum of the cathodic peak of polythiophene was found around lambda = 500 nm (2.5 eV), depending on the applied potential. It is in agreement with the results of UV-vis optical spectra of deposited layers and of pressed pellets. The flatband potential of polythiophene in the heterojunction with TiO2, obtained from photocurrent measurements, was 0.53 V-SCE. (C) 2005 Elsevier Ltd. All rights reserved.