In the context of investigations on drug diffusion into human skin, first examples of using porous filters as model bio-membranes to understand the role of physical and chemical parameters on the penetration of chromophores. The diffusion of small molecules has been investigated in porous filters of different pore sizes by using pulsed photoacoustic spectroscopy. An analogy is made between the model membranes and human skin concerning the influence of the filter structure and the hydrophilic nature of the matrix support material, Finally, first data are presented on the effect of a modified surface filter structure on the diffusion pattern, thus opening the field to the potential use of these filters as model membrane of adjustable structural and chemical parameters.