In the present work the effect of surface modification by rhodium on the conductivity response of the SnO2 films to reducing gases such as CO and H-2 and oxidizing gas ozone was analyzed. SnO2 films, subjected to surface modification, were deposited by spray pyrolysis, while Rh was deposited using a micro electron beam evaporation. The thickness of the Rh coating varied in the range of 0-0.1 ML. It was found that there is an optimal thickness of Rh, which gives an improvement in the sensor response and a decrease in the recovery time. An explanation of the observed effects was proposed. It was assumed that the atomically dispersed state of rhodium is most active in gas-sensing effects. The transformation from the atomic state to the cluster state reduces the efficiency of the surface functionalization of SnO2 with rhodium.