A mathematical model for the gas permeation in ceramic membranes (support and supported separation layer) is proposed. The model is based on the relationship between the structure parameters of the porous material and the gas permeability. This procedure makes it possible to determine the mean pore radius, r, and geometric factor (ratio of porosity and tortuosity), Psi, of the support and the supported layer. The model was verified with the membrane supports made of ct-aluminum oxide. The results were compared with the mercury porosimetry measurements.