Mono- and bilayer adsorption of H2O molecules on TiO2 and SnO2 (110) surfaces has been investigated using static planewave density functional theory (PW DFT) simulations. Potential energies and structures were calculated for the associative, mixed, and dissociative adsorption states. The DOS of the bare and hydrated surfaces has been used for the analysis of the difference between the H2O interaction with TiO2 and SnO2 surfaces. The important role of the bridging oxygen in the H2O dissociation process is discussed. The influence of the second layer of H2O molecules on relaxation of the surface atoms was estimated.