Method for determining a spatial distribution k x, y f of a parameter of interest (k) representative of a permeability of a diffusion layer of at least one electrode of an electrochemical cell, said cell including two electrodes separated from each other by an electrolyte and placed between two bipolar plates suitable for bringing reactive species to the electrodes and for removing the heat produced by the cell in operation, at least one electrode including a diffusion layer suitable for ensuring the diffusion of a reactive species as far as the electrolyte, said method comprising the following steps: i) providing (110; 210) an electrochemical cell, within which the parameter of interest (k) is distributed with an initial spatial distribution k x, y i and for which the spatial distribution of a temperature within the electrochemical cell in operation has at least one local value higher than or equal to a preset maximum local value; ii) defining (120; 220) a spatial distribution T x, y c of a set-point temperature (T c) within said electrochemical cell in operation, said distribution being such that the local temperature values are lower than preset maximum local values; iii) measuring (130; 230) a spatial distribution D x, y r of a first thermal quantity representative of the local removal of heat (D r) within said electrochemical cell in operation; iv) estimating (140; 240) a spatial distribution Q x, y e of a second thermal quantity (Q e) representative of the local production of heat (Q e) within said electrochemical cell in operation, depending on said spatial distribution T x, y c of the set-point temperature (T c) and on said measured spatial distribution D x, y r of the first thermal quantity (D r), so that the spatial distribution of the temperature of said electrochemical cell in operation, the first thermal quantity (D r) of which cell having said measured spatial distribution D x, y r and the second thermal quantity (Q e) of which cell having said estimated spatial distribution Q x, y e, is substantially equal to that T x, y c of the set-point temperature (T c); and v) determining (150; 250) a spatial distribution k x, y f of the parameter of interest (k) depending on the spatial distribution Q x, y e of the second thermal quantity (Q e). i) providing (110; 210) an electrochemical cell, within which the parameter of interest (k) is distributed with an initial spatial distribution k x, y i and for which the spatial distribution of a temperature within the electrochemical cell in operation has at least one local value higher than or equal to a preset maximum local value; ii) defining (120; 220) a spatial distribution T x, y c of a set-point temperature (T c) within said electrochemical cell in operation, said distribution being such that the local temperature values are lower than preset maximum local values; iii) measuring (130; 230) a spatial distribution D x, y r of a first thermal quantity representative of the local removal of heat (D r) within said electrochemical cell in operation; iv) estimating (140; 240) a spatial distribution Q x, y e of a second thermal quantity (Q e) representative of the local production of heat (Q e) within said electrochemical cell in operation, depending on said spatial distribution T x, y c of the set-point temperature (T c) and on said measured spatial distribution D x, y r of the first thermal quantity (D r), so that the spatial distribution of the temperature of said electrochemical cell in operation, the first thermal quantity (D r) of which cell having said measured spatial distribution D x, y r and the second thermal quantity (Q e) of which cell having said estimated spatial distribution Q x, y e, is substantially equal to that T x, y c of the set-point temperature (T c); and v) determining (150; 250) a spatial distribution k x, y f of the parameter of interest (k) depending on the spatial distribution Q x, y e of the second thermal quantity (Q e).