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.