Structural and surface properties of two commercial polysulfone ultrafiltration membranes have been evaluated by different techniques. Pore size distributions have been determined by Liquid-Liquid Displacement Porosimetry (LLDP) as well as by image analysis performed onto Field Emission Scanning Electron Microscopy (FESEM) images of the membrane surfaces. Fourier Transform Infrared Spectroscopy (FTIR) has been used to investigate membrane composition, and in particular, to obtain proper information on the presence of an additive within the membrane structure. Porosimetric results obtained by the two independent techniques compared reasonably well and the Molecular Weight Cut Off (MWCO) of the two membranes estimated from LLDP pore size distribution was found to be in good agreement with the nominal values given by manufacturers. (C) 2014 Elsevier B.V. All rights reserved.