In this work we demonstrate the use of computerized x-ray micro-tomography and numerical simulations in evaluating ﬂow permeability of ﬁbrous porous materials. This ab-initio approach involves solving ﬂuid ﬂow through material samples in the actual pore space obtained by tomographic techniques. The procedure is applied here in three different materials, namely plastic nonwoven felt, newsprint and wet pressing felt. All numerical results presented are compared with experimental data for the same materials. The non-woven felt material, having a relatively simple structure, is ﬁrst used as a test case for comparing two different numerical schemes, lattice-Boltzmann method and a ﬁnitedifference method. Here, values of both transverse and in-plane permeability are obtained. The transverse permeability of newsprint and wet pressing felt under varying degree of compression is then found using lattice-Boltzmann method. Finally, we apply the same approach in estimating permeability in different structural layers of the wet press felt material. These material parameters are laborious or even unfeasible to determine experimentally. The procedure is applicable e.g. in ﬁnding the relevant material parameters for macroscopic models describing calandering, drying and wet pressing processes.