It has been shown that the hydrogen photochromism, i.e., photochromism arising in WO3 films due to hydrogen atoms detached from hydrogen donor molecules under the action of light, is massively impacted by proton diffusion. The control of the diffusion can be established by the combined use of two types of hydrogen-containing molecules; one (organic) playing the role of the hydrogen donor, whereas the other (water) provides pathways for the proton diffusion. The film morphology highly influences formation of the proton conducting water wires in pores of the WO3 films. The spirit is that the hydrogen photospillover is used here: the hydrogen atoms detached from the hydrogen donor molecules adsorbed on the surface of the highly disordered WO3 films flow to the polycrystalline WO3 films along the special water pathways that are formed in the highly disordered films. The hydrogen spillover triggered by light makes it possible to create the photochromic systems with enhanced photochromic sensitivity and special optical characteristics of the photochromic state. (c) 2013 Elsevier B.V. All rights reserved.