For dispersed transition metal oxides, the specific catalytic activity in the reactions of CO and hydrocarbons oxidation was compared with the densities of bulk and surface defects that were estimated using a combination of; diffraction and spectroscopic methods. On this basis, the oxide systems were classified with respect to the scale and origin of the structural sensitivity manifestation. The results were discussed from the point of view of the atomic structure of the most developed surface faces of these oxides and their stoichiometry ranges. The most active surface sites were found to be associated with the surface extended defects including those located at the outlets of bulk extended defects.