The adsorbed oxygen species formed upon the reoxidation of reduced titanium dioxide (Degussa P-25) and oxygen adsorption on the reduced and reoxidized titanium dioxide are studied by thermal desorption mass spectrometry. The reoxidation of the oxide in the presence of O2 at P ≥ 2 × 10–3 Pa and T ≥ 500 K is shown to result in the appearance of a peak with a maximum at ∼700 K in the thermal desorption spectrum. The desorption of oxygen corresponding to this peak occurs via the recombination mechanism with the activation energy Edes = 1.4 eV. The dynamic model of reoxidation occurring through the adsorption and desorption of oxygen is suggested for the explanation of the temperature dependences of the concentration of surface oxygen that were obtained earlier for the process of reoxidation of rutile single crystal.