The way that the Au precursor, the TiO2 support and the sodium citrate is added to the ethylene glycol/water strongly influences the Au nanoparticles sizes of the obtained Au/TiO2 catalysts. The values of CO conversion, CO2 selectivity and O2 consumed were also greatly influenced by the size of Au nanoparticles, so that the values increase as the sizes decrease. Also, the increase of these values occurs at lower temperatures with decreasing particle size. The influence of some synthesis parameters, such as the use of different Au precursors, the Au citrate molar ratio, the pH of the reaction medium and the use of higher boiling alcohols (glycerol, diethylene glycol) as solvent could be investigated in order to further reduce the size of Au nanoparticles.