We present for the first time a theoretical investigation on the reactivity of the different oxygen sites in a dispersed V2O5/TiO2 slab model. Our model represents anhydrous conditions and contains all the potentially active oxygen sites proposed to date in the literature: vanadyl V=O, bridging V-O-V, interface V-O-Ti, and surface Ti-O-Ti oxygen sites. Geometric features are analyzed in terms of bond distances and site accessibility. Projected density of states diagrams show a decrease of the band gap for the supported system with respect to pure anatase (001). The most energetic levels of the valence band correspond to the oxygen atoms in the V2O5 unit, although a further decomposition in terms of mono- and dicoordinated oxygen is not obvious. Atomic hydrogen adsorption on the different sites is tracked. The most exothermic systems are those where H adsorbs on the V2O5 oxygen sites due to their higher basicity regarding pure anatase. The heats of adsorption referred to atomic H are V-O-Ti (2.95 eV) > V=O (2.60 eV) > V-O-V (2.17 eV) > Ti-O-Ti (2.07 eV). This means that the most reactive sites are those located at the interface between the V2O5 and the TiO2 unit, while the vanadyl V=O bonds are more stable and would react at a lower extent in hydrogen atomic adsorption. Relaxation makes the adsorption energy decrease: the support relaxes less when hydrogen adsorbs than for the bare V2O5/TiO2 System. H adsorption forms hydroxyl OH bonds by reduction of the vanadium atom, even when the adsorption site is located on the TiO2 surface sites.