TiO2 nanotubes were produced by self-organized electrochemical oxidation of Ti. The tubes were N-ion implanted at two nominal fluencies, 1 x 10(15) and 1 x 10(16) ions/cm(2). Implantation was carried out into amorphous and crystalline (anatase) tubes. Photoelectrochemical, SEM and XRD measurements show successful doping at a dose of 1 x 10(16) ions/cm(2), however the ion implantation process causes strong structural alterations. Amorphous tubes show a disintegration of the morphological integrity, while anatase tubes are 'amorphized'. This amorphization leads to a decrease of photoresponse in the UV range, but the N-doping results in a strong sub-band gap response. (c) 2005 Elsevier B.V. All rights reserved.