This work compares the behaviors of TiO 2 nanotube (TNTs) array obtained by anodization of Ti foils in an ethylene glycol/NH 4 F/ water electrolyte with different applied voltages during a constant anodization time, and for the same electrolyte composition. The crystal structure and surface morphology of the annealed anodic fi lms are investigated by X-Ray diffraction system, Raman spectroscopy and scanning electron microscopy, respectively. The TiO 2 nanotubes obtained at potentials of 20 - 40 - 60V show different inner diameters (42 - 89 - 124nm), tube length (1.2 - 3.3 - 12.7 μ m) and wall thicknesses (12 - 15 - 18nm). The in fl uence of these geometric parameterson the photoelectrochemical properties and the photocatalytic activity were investigated in detail. The results showed that the photocatalytic performances of TNT fi lms are improved when the speci fi c surface, the tube length and the solid fraction are increased, but the increase is slowed down when a limiting thickness of the layer is reached. The surface states which usually show high density in nanostructured layers do not seem to in fl uence signi fi cantly the photocatalytic activity of the layers.