Article deals with pore size distribution assessment of porous materials using image analysis. Test samples used in the study were prepared from metal foams and porcine trabecular bone. Two- and three- dimensional images were obtained by SEM (scanning electron microscopy) and a high resolution flatbed scanner. For the pore size distribution assessment various methods were used, depending on input data properties (method of obtainig image data) and on pores characteristics (different approach should be used for closed or opened pores). For pore size evaluation using 2D images 25F Association method [5] was used. For verification of the developed algorithms MIP (mercury intrusion porosimetry) [6] measurements were performed, but only in case of trabecular bone samples, because opened pores are necessary for these measurements. Presented algorithms were verified using artificial data structures (binary images with controlled pore- size distribution).