We present periodic DFT calculations for studying the metal atom adsorption, mainly of the first metal transition series, on an O-defective TiO 2 support. The presence of a vacancy does not anchor the metal. The adsorption energy is weaker than on the non-defective surface and the favored adsorption sites remains the surface oxygen atoms. This is related to the reducibility of the titanium. Reduction electrons are more stable and less reactive than for MgO. They are not always localized in the vacancy. Even when localized there, the formation of Ti–M bonds is not competitive with that of O–M bonds.