The electrochemical characterization of mixed oxides containing cobalt and nickel prepared by cathodic electrodeposition is presented. Their catalytic properties are discussed according to the results obtained employing stationary polarization curves, voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. Impedance results were analyzed considering a porous electrode and approximated in terms of a finite transmission line model of conical pores linked in parallel. For sake of comparison, results obtained with Co-Ni cobaltites prepared by thermal decomposition are also presented. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.