Hot filament chemical vapour deposition (HFCVD) technique was applied to deposit a porous tungsten oxide film on glass wafers. The tungsten filament was used as a source in a vacuum atmosphere. The porous film was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray thermodiffraction, nitrogen sorption and small-angle X-ray scattering. From these characterization techniques it was found that porous film presents a clusters-like morphology of WO3-x particles. The particles are arranged on substrate in a way that free spaces are originated, as a 3D network of pores. By increasing temperature, the BET specific surface area of the porous film changes from 38.67 to 34.5 m(2) g(-1) most likely due to the particles have a tendency to stick together to form aggregates, particularly at high temperature. A fractal geometry approach permits to elucidate the interconnection between the particles and a simple model of the porous structure is proposed. (C) 2009 Elsevier B.V. All rights reserved.