Electrical and structural properties of TiO2 thin films deposited at room temperature by reactive DC sputtering have been investigated on three different substrates: high resistivity (>1000 Ωcm) float zone Si(111), float zone Si(100) and alkali free glass. As-deposited TiO2 films on glass substrate showed extremely high resistivity of (∼5.5×103 Ωcm). In contrast, lower resistivities of ∼2 Ωcm and ∼5 Ωcm were obtained for films on Si(111) and Si(100), respectively. The as-deposited films were found to be oxygen-rich amorphous TiO2 for all the substrates as evidenced by X-ray photoemission spectroscopy and X-ray diffraction. Subsequent annealing led to appearance of anatase TiO2 on Si but not on glass. The surface of as-deposited TiO2 on Si was found to be rougher than that on glass. These results suggest that the big difference of electrical resistivity of TiO2 would be related with existence of more anatase nuclei forming on crystalline substrates, which is consistent with the theory of charged clusters that smaller clusters tend to adopt the substrate structure.