Nanostructured ceria-alumina mixed oxides containing different concentrations of ceria (10 and 30 wt.%) were prepared by the sol-gel method using organo-metallic precursors of alumina and ceria. The size of alumina and ceria particles in the prepared Ce-Al-O mixed oxides was smaller than that of pure alumina or ceria. The gold catalysts (3 wt.% Au) supported on ceria-alumina mixed oxides by deposition-precipitation (DP) using HAuCl4 and urea were characterized by several techniques: TEM, XPS and UV-vis spectroscopy, and temperature programmed reduction/oxidation (TPR/TPO). The catalytic activity of prepared Au/CeO2-Al2O3 catalysts in CO oxidation was higher than that of Au/Al2O3 and Au/CeO2 catalysts. Nanostructured ceria incorporated into an alumina matrix has been found quite effective for gold species activation in CO oxidation. In fact, transient analysis of CO oxidation provided an estimate of the relative content of (Au-ceria vacancy) active sites in catalysts. Obtained values are in good agreement with the order of activity for tested samples and gold dispersion according to EXAFS data. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.