The effect of support geometry on the performance of asymmetric ceramic membranes for gas separation is analyzed. Flat plate (FP), tubular (TU) and multichannel (MC) geometries are investigated using the dusty gas model (DGM) to describe transport of a multicomponent gas mixture through the macroporous support. It is shown that: (a) the support geometry significantly affects membrane performance; (b) in the case of the multichannel geometry, the inner channels do not contribute efficiently to the overall gas transport; (c) best performance in terms of both flux and permselectivity is obtained for tubular geometry. It is furthermore clarified that for an accurate description of the transport behaviour it is crucial to properly account for the relative contributions of all different transport mechanisms (Knudsen diffusion, bulk diffusion and viscous flow) included in the DGM. (C) 2004 Elsevier B.V. All fights reserved.