The WO 3 films were grown in 0.1M HClO 4 aqueous solution, at different formation potentials (E f ) in the range of 2.0–7.0V versus sce, on W electrode. The anion diffusion coefficient (DO) of WO 3 films was calculated from EIS spectra, following the surface charge approach (at high-field limit approximation), the Point Defect Model and the Mott–Shottky analysis. Among the parameters necessary to evaluate DO, the half-jump distance (a) is very relevant, given that a small variation in a has a great impact in the calculation of DO. In this work, it is proposed the half-jump distance (a) should be evaluated from spectroscopic data (available in the literature). The value of a (∼1.9Å) is taken from lattice constants of a-WO 3 (amorphous-WO 3 ), with different values of N (coordination number), and the lattice constants of m-WO 3 (monoclinic-WO 3 ). The calculated value of DO was ∼3×10 −17 cm 2 /s.