Changes in AC electrical conductance were used to obtain information on the peculiarities of propene interaction with the surface of polycrystalline tin dioxide. As results from in situ electrical conductivity data, adsorption of propene seems to prevail over oxygen adsorption, when both reactants are present. The influence of residual humidity suggests the involvement of surface hydroxyl groups in the mechanism of adsorption/oxidation as a possible source of oxygen. The strong adsorption of propene is facilitated by the low mobility of the bulk lattice oxygen of tin dioxide up to 400 degrees C which in turn determines the surface proton mobility coupled with the ability of this material to catalyze dehydrogenation.