The results of density functional theory (DFT) calculations of the electronic structure of TiO2 and of the binding of Au and Au2 to stoichiometric and defective TiO2. surfaces are presented. As such, the calculations on clean TiO2 differ from the previous ones mainly because a larger supercell is used. This allowed to get some understanding of the interactions between vacancies and to study how localized are the electrons left behind when a neutral oxygen atom is removed.