The effect of titanium hydride on the formation of nanoporous TiO2 on Ti during anodization has been investigated by X-ray photoelectron spectroscopy, grazing incident X-ray diffraction, transmission electron microscopy and scanning electron microscopy. Titanium hydride (TiH2) was formed after cathodization, profoundly impacting the formation of nanoporous TiO2 on Ti by anodization. Oxide layer and nanocrystal structure were observed after anodization with cathodic pretreatments. A multi-nanoporous TiO2 layer was formed on the titanium. The titanium hydride is a nanostructure. The nanostructure is directly changed to nanoporous TiO2 by a dissolution reaction during anodization. The nanoporous layer is difficult to form without cathodization. The nanostructural TiH2 is important in forming a nanoporous TiO2 layer. Anoclization treatment with cathodic pretreatment not only yields a titanium surface with a multi-nanostructure, but also transforms the titanium surface into a nanostructured titanium oxide surface. (c) 2006 Elsevier B.V All rights reserved.