In this article the pore structure and porosity parameters of polycaprolactone (PCL) nano-microfibrous scaffolds are investigated using a predicting theoretical model and a nondestructive evaluation approach based on confocal laser scanning microscopy (CLSM) and three-dimensional image analysis. Different fibrous scaffolds with different fiber diameters produced by electrospinning process and their 3D–pore structure were evaluated theoretically and also compared to results of CLSM and capillary flow porometery methods. The effect of polymer concentration on the pore structure of scaffolds was also investigated. The results showed that, the introduced approach not only can measure the pore size distribution of nanofibrous scaffolds, but also can measure pore interconnectivity of fibrous scaffolds. Furthermore, the results showed that increasing the fiber diameter resulted from increasing the polymer concentration in solvent can effectively increase the pore dimensions within the scaffold structure. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 903–910, 2014.