The preferential oxidation of CO to CO2 in a simulated reformed gas using Au/-CeO2-ZrO2 catalysts was examined. The studied catalyst showed high catalytic activity and stability during long-term tests even in presence of CO2 and water vapour, which inhibited the conversion of CO to a small extent. The catalyst preparation at controlled pH (6) favours the high dispersion of deposited gold particles, while the catalytic activity and selectivity was correlated with the size and oxidation state of gold particles. Furthermore, it was observed that oxidizing treatment resulted in the formation of gold particles having different shapes and/or side length, which was evidenced by a broadening of the plasmon resonance band (From DRS UV-vis). Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.