Using density functional and STM theory we model the images of TiO2(110), its defects, molecularly adsorbed water, its recently suggested pseudo-dissociated precursor and final dissociation product. The simulated STM images and the corresponding line scans agree with the available experimental data: oxygen vacancies are imaged as smaller protrusions than unpaired or paired hydroxyl groups. Finally, we obtain simulated images of undissociated and pseudo-dissociated water molecules. These simulations are discussed in view of their appearance in the experiments. (c) 2007 Elsevier B.V. All rights reserved.