A new procedure for quantitative characterization of different types of solid materials is proposed. The technique is based on the Scanning Electron Microscopy (SEM) analysis results of porous materials and their processing by the software ImageJ. Several types of porous adsorbents AX21, AC35, GAC250, ACENO and IRH3 activated carbons were investigated. Based on SEM analysis, different characteristics of the samples such as porosity, pore size distribution, bed particles porosity can be obtained. In this study, the particle size, the average macropore size and pore size distributions (PSD) of samples were determined with a new procedure for SEM analysis treatment using ImageJ software. Three distribution functions (Gamma, Weibull and Lognormal) were selected to describe the experimental results. The Lognormal distribution fitted more accurately the experimental data.