SiO2-supported Au nanoparticles derived from sol were promoted with 0.04–7.4 wt % CeO2using two methods. The addition of Ce precursor was done directly to the Au sols before sol immobilization step (method A) or to the suspension of parent Au/SiO2(method B). Both preparation routes resulted in CeO2decoration of 1–3 nm over Au nanoparticles, which induced high CO oxidation activity. However, above 0.6 wt % CeO2content, the activity did not change significantly, but it greatly exceeded that of pure Au/CeO2used for reference. High-resolution transmission microscopy (HRTEM) showed that up to this concentration ceria patches are attached onto gold surface, and the further increase in Ce-loading caused CeO2spread over the support surface as well. Strong interaction of Ce species with stabilizer ligands located around Au is suggested as the reason for CeO2localization on gold.