The simulation of the random porous network of five samples of functionalized SiO2 took place using a dual-site-bond model (DSBM) and Monte Carlo techniques for achieving the proper arrangement of the pores into the system. The simulation took place in 7 x 7 x 7 lattice. As a starting point of simulation the adsorption branch of N-2 isotherm was considered from which the pore size distribution was estimated. Then as a benchmark of simulation the N-2 desorption branch was considered whose fitting was achieved using the Monte Carlo technique for selecting the proper place of each pore into the 7 x 7 x 7 lattice. From the obtained model, it was possible to estimate the distribution of pore connectivities of each system. The mean value of those connectivity distributions tallies with the corresponding mean values estimated using the standard methodology of Seaton. In addition, the mean tortuosity of the porous network was estimated and the results were favorably compared with values of tortuosity estimated recently via the so-called corrugated-pore-structure-model (CPSM) for the same solids. The degree of functionalization of the parent SiO2 affects both connectivity and tortuosity in a linear way. Some discrepancies observed between the results obtained via this methodology and the ones obtained using the Seaton or the CPSM model are discussed. (C) 2004 Elsevier Ltd. All rights reserved.