With the study of composite materials based on the In2O3-SnO2 pair, we look for better sensitivity and selectivity to the gases, than those of the sensors made out of only one of those metal oxides. This would be due to the fact that some of the interstitial positions that were initially occupied by the atoms of one of the metals are now occupied by atoms of the other metal: if the single covalent/ionic adsorption is decisive in the observed changes in the materials conductivity, then the electronegativity of the occupying metal atoms may be used to regulate the sensitivity and selectivity. We will present the results obtained for a film obtained by sol-gel method and deposited using a slow spin coating process, of the In2O3-SnO2 pair, with a 2:3 mol ratio of Indium and Tin, respectively. The rather involved behaviour of our sample is understood by measuring their complex impedance subjected to an external sinusoidal varying electric field, which is being applied in the presence of different relative humidities, at various working temperatures. The main goal of this work here described is the study of the relative humidity influence on the sensing properties of the composite thick film.