This article is focused on assessment of pore size distribution of a porous material. Improvements of the analysis procedure and of the software tools are presented. For the comparison of reliability of the presented method specimena of various origins were tested. As representatives of biological materials specimena of human and porcine trabecular bone were tested, as representatives of artificial materials synthetic pumice and frit glass were used. Images required for the image analysis were captured using a CCD camera, a high resolution flatbed scanner and a confocal microscope. The different methods used to acquire the images are discussed regarding to the range of the pore size, dimensions of the available specimen and properties of the specimen surface. Used image processing algorithms were tested and improved regarding to the variable shape of the voids present in the material structure.