Abstract Porous titania, TiO 2, films on Ti substrates were prepared electrochemically. The adsorption of biologically compatible ions, like calcium and phosphate ions, on the formed TiO 2 films was investigated by electrochemical impedance spectroscopy, EIS, and electron diffraction X-ray, EDX, techniques. The morphology of the formed oxide films and the adsorbed layers on their surfaces was investigated by the scanning electron microscopy, SEM. The experimental impedance data were fitted to theoretical data according to proposed equivalent circuit models. The impedance data fitting enabled the explanation of the structure of the oxide film and the adsorption phenomena occurred on its surface. The film characteristics under different conditions were discussed and the adsorption of Ca 2+ and PO 4 3− was explained. The results have shown that the oxide films formed potentiostatically on Ti in H 2O 2 containing H 2SO 4 are capable to adsorb biologically compatible ions. The adsorbed layer thickness was found to increase with the increase of concentration of calcium ions present in the ambient electrolyte. The biocompatibility of these materials depends essentially on the apatite-forming ability of TiO 2 due to calcium ion incorporation in the adsorbed films. The formed oxide films with the relatively thick apatite-like adsorbed layer are good implants for bone surgeries and dental applications.