Highly porous nonwovens composed of nanofibers and produced by electrospinning are key elements in a broad range in technical but also in Life Science areas. Applications for gas or fluid filtration, textile applications, carriers for catalysts and scaffolds for tissue engineering are selected examples. These applications require well defined nonwoven parameters such as in particular pore diameters, internal surfaces as well as permeation properties. Electrospinning, on the other hand, allows to control structural parameters such as fiber diameter, nonwoven architecture as well as in certain limits the total porosity. It is thus highly important to know as much as possible about the correlations between the structural parameters controlled by electrospinning and the parameters controlling the performance of the nonwovens composed of the electrospun nanofibers. In the present contribution we analyze these correlations for different types of electrospun nonwovens for a broad range of fiber diameters on an experimental scale The nonwoven considered are composed of polyacrylonitrile (PAN) and polyamide 6 (PA 6) fibers. Results are that pore diameters, specific surface area and permeation coefficients scale in a transparent way with fiber diameters. Finally we briefly compare these experimental results with corresponding predictions gained for ideal nonwovens predominantly from Monte Carlo simulations. The results suggest that one is able to design electrospun nanofiber based nonwovens with predetermined properties and functions in a highly controlled way. (C) 2010 Elsevier Ltd. All rights reserved.