Platinum was deposited onto pure alumina as well as on alumina modified by addition of 7 and 15 wt.-% barium. The alumina hydroxyl groups were neutralized by barium addition and the surface of the modified support had a basic character. The introduction of barium decreased the accessible platinum area because of a sintering of the metal particles associated with a partial coverage of the platinum crystallites by barium containing species. In addition, the platinum surface atoms were electron-enriched. As a consequence the catalytic activity of alumina supported platinum was lowered in the presence of barium. Nevertheless, the turn-over numbers were not strongly modified by the barium additive, suggesting that the catalytic properties of accessible platinum atoms were not sensitive to the electronic effect induced by barium addition.