Polyurethane (PU) solved in dimethylformamide (DMF) was electrospun under one set of conditions using five different Supporting textiles. The mechanical properties of the nanofiber mats were measured by the Sentmanat extensional rheometer, and the pore size distribution was calculated by a newly Proposed digital image analysis methodology applied on nanoscale SEM images taking macroscopic features of the nonwovens into account. It has been found that supporting textiles have a very high effect on mechanical properties of nanofiber mats (even if their fiber diameter distributions are similar), which can be explained by different porosity of the prepared samples. (C) 2009 Elsevier Ltd. All rights reserved.