A polycrystalline palladium foil and palladium films of various thickness, supported on oxidized silicon wafers, were treated under catalytic conditions in a gas-flow reactor. Their topography and chemical composition were investigated before and after exposure to oxygen and hydrogen by atomic force microscopy and X-ray photoelectron spectroscopy. The results were compared with those of nanostructured palladium model catalysts measured under the same conditions. The nanostructured samples were prepared on oxidized silicon wafers by laser interference lithography and subsequent metal evaporation. Hydrogen and carbon monoxide oxidation were used as test reactions in a quartz reactor at 1 atm pressure and at temperatures up to 600 degrees C. All palladium-containing systems were catalytically active after several activation cycles. Nanostructured silver model catalysts were treated in the same way for comparison. The high-temperature treatment at atmospheric pressures in oxygen and hydrogen proved to be highly effective in decontaminating the surface of the catalysts and especially in ridding it of carbon-containing species. Significant changes in the topography of the metal surfaces due to catalytic etching were observed after treatments at 400 and 600 degrees C in the presence of oxygen and hydrogen. While larger palladium clusters on the flat SiO2 surface tended to sinter and form larger aggregates, the silver particles started to split and spread over the substrate.