This report presents results related to the preparation of Au/ZnO using the deposition-precipitation technique. Many samples were synthesized taking into account different pH values, gold concentration, procedures and contact times between the gold precursor and support. The exposure of gold compounds to radiation in the visible range was also examined during the preparation. These syntheses show that precipitation-deposition is, in this case, an ionic exchange. It could be observed that exposure to light and competition among anions change the gold content of the catalyst. Therefore, these are important parameters in the preparation of gold catalyst by ionic exchange. The results also show that by using this technique it is possible to prepare active catalysts for the preferential oxidation of carbon monoxide (PROX) reaction. (C) 2008 Elsevier B.V. All rights reserved.