Nanocrystalline films of metal tin with a thickness of 30, 100 nm were annealed in the air for 1 h at constant temperatures varying from 170 to 750 degrees C. Transmission electron microscopy and X-ray absorption near edge structure experimental data show the dependence of phase composition not only on the temperature of treatment but also on the thickness of initial metal layer. Optical investigations of absorption show a considerable dependence of position of the fundamental edges on the thickness of the films. The observed maxima of absorption at similar to 3.6 eV are related with the defect states, mainly, with oxygen vacancies of non-stoichiometric oxide. (C) 2006 Elsevier B.V. All rights reserved.