The structure of platinum species in a model set of monodisperse Pt/gamma-Al2O3 catalysts was studied using radial distribution function (RDF) of electron density. Catalyst preparation conditions were revealed to considerably affect the dispersion and structure of supported platinum. Cation vacancies on the gamma-Al2O3 surface were essential to anchor electron deficient platinum atoms and clusters. Platinum segregation with forming finely dispersed metal particles was evident in some catalysts. The methane total oxidation over the Pt/gamma-Al2O3 catalysts was established to depend strongly on the platinum oxidation state. The catalysts containing oxidized platinum species and highly dispersed oxidizable Pt-0 particles were more active. The metal-support interaction improved the performance of the catalysts indirectly, by stabilizing the platinum dispersion. (C) 2014 Elsevier B.V. All rights reserved.