Nitrogen-doped TiO2 nanoparticles have been prepared by the IR laser pyrolysis technique. A sensitized mixture of TiCl4 (vapors) and N2O was used as titanium and nitrogen precursors, respectively. The structural properties of the resultant N-doped nanoparticles such as the phase formation and the average particle size and distributions were investigated by X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. The phase composition varied from almost pure anatase to mixtures of rutile and anatase. A decrease of the mean particle diameters from about 18 nm in case of the almost pure anatase sample to about 13 nm in case of the anatase-rutile mixture is observed. XPS analysis suggests and interstitial character of the doping process. (C) 2008 Elsevier B. V. All rights reserved.