Isothermal ellipsometric measurements were carried out under controlled vapour pressure of ethanol from vacuum to saturation on mesostructured anatase-based thin layers. Thin films were prepared by the sol-gel route using the templating effect of lyotropic mesophases. Ellipsometric porosimetry (EP) has been applied for analysing thermally treated films with an ordered mesoporosity resulting from the removal of the template. The EP results are discussed and correlated with those obtained by nitrogen adsorption using a conventional volumetric apparatus and TEM analysis. (c) 2005 Elsevier B.V. All rights reserved.