Diffusion of Li and Na ions in TiO2, anatase, has been studied using theoretical (quantum chemical nb initio periodic Hartree-Fock and a modified semiempirical INDO) as well as electrochemical (chronocoloumetry) methods. On the basis of the theoretical calculations, the geometry of equilibrium and transition states for the impurities as well as the crystalline framework are analyzed and discussed. The calculated activation energies for Li+ and Na+ diffusion were found to be only slightly higher than 0.5 eV by both theoretical methods. The agreement of either theoretical method with the electrochemical experiments, 0.60 and 0.52 eV for Li+ and Na+, respectively, is also : remarkably good.