Dependence of catalytic activity in CO oxidation on the structure of gold nanoparticles supported on various TiO2 polymorphs has been investigated. Pure brookite, brookite-anatase (45: 55) and anatase-rutile (85:15) mixtures were compared as supports of Au/TiO2. Au nanoparticles were deposited on different TiO2 supports by adsorption of Au colloids of about 6 and 15nm mean diameter and by deposition precipitation (DP) with urea providing Au particles smaller than 5 nm in size. Sol derived gold particles were more stable against sintering on brookite than on anatase containing supports. Taking into account the particle sizes of gold and titania for all types of gold deposition methods, the Au-anatase perimeter seems to be significantly more active in CO oxidation than the Au-brookite perimeter. The difference in activity should be originated from the different electronic, physical and surface properties of anatase and brookite. (C) 2010 Elsevier B. V. All rights reserved.