Pure and Pd-doped polycrystalline SnO2 thin films have been synthesized by a modified chemical vapour deposition process using the pyrolysis of an aerosol generated by ultrahigh frequency spraying of a volatile precursor solution. The depositions have been carried out on oxidized [100] silicon. Growth rate, microstructure and composition of the films are well-controlled by the deposition temperature (460-560-degrees-C) and the moisture of the carrier gas. Palladium particles (metal or oxide) are dispersed on SnO2 grains. At low temperature the moisture increases the growth rate of tin oxide without increasing the palladium one. The influence of adsorption phenomena on the surface composition has been studied by annealing under ethanol and CO, and afterwards by analysing Sn, 0 and C contents by Auger spectroscopy. The heat treatments induce an increase of 0 and C concentration. The introduction of palladium in the films largely increases the gaseous adsorption, showing a maximum at low temperature. These results are correlated with electrical conductance measurements, showing the influence of CO adsorption on electrical properties.