Nanocrystalline TiO2 (anatase) has attracted considerable interest for applications in photoelectrochemical solar cells. This device is based on charge injection from photoexcited organometallic dye which is adsorbed on the TiO2 surface. Titanium dioxide can electrochemically accommodate Li+ which is useful for a design of new Li-ion batteries. Whereas the charge storage in anatase or rutile is based on the Li-insertion into the bulk crystal, the monoclinic TiO2(B) exhibits an unusual pseudocapacitive Li-storage mechanism. The photoelectrochemical and Liinsertion activity of mesoscopic TiO2 depend significantly on the electrode morphology.