A model is proposed for the mechanism of reaction of the hydrated electron with strongly oxidizing inorganic oxocompounds, according to which such reactions comprise three steps: (1) a primary split-off of O- occurring immediately upon the transfer of the electron to the oxocompound, (2) after which O- becomes fully solvated, acquiring properties as in the bulk phase, and (3) finally, the solvated O- either escapes from the cage or forms an electron adduct by reacting back within the cage with its partner. The model is based on studies of the photochemistry of aqueous solution of the oxoanions O-3(-) and ClO3- (Walhaut, P. K.; Silva, C.; Barbara, P. F. J. Phys. Chem. 1996, 100, 5188. Klaning, U. K.; Sehested, K. J. Phys. Chem. 1991, 95, 740.), which suggest that solvation of the photoproduct O- precedes cage-back reactions. Measurements of the reactions of the hydrated electron with the perbromate ion and the periodate ion and of the reactions of O- with the bromate and iodate ion support the model by verifying that no electron adduct is formed unless O- and its partner react in the bulk phase at a diffusion-controlled rate.