Natural gas (methane) production from coal seams is recognized as one of the valuable energy sources due to high storage capacity of coal to store gas at low pressures. It is known that coal composition, pore structure, and mineral matter properties affect both the amount of adsorbed quantity and kinetics of adsorption when the coals are considered for natural gas production or mediums for storing gas, mainly methane or carbon dioxide. Experiments in the held of adsorption equilibrium and dynamics usually investigate the adsorption properties on crushed coal samples within a certain range of particle sizes. This data can be used to obtain an average behavior representing the very heterogeneous coal-gas system. But, although individual pores are not likely influenced by crushing, this process destroys the natural integrity and continuity of the porous medium and mixes all the lithotypes and minerals in the same batch. This makes it impossible to investigate and differentiate the behavior of different microstructures and lithotypes. In this study, gas transport and adsorption were investigated on a 3.8-cm diameter core of a medium volatile bituminous coal from Gelik seam in the Zonguldak Basin (Northwestern Turkey) by using quantitative X-ray computerized tomography (CT) imaging technique to visualize the interior of the coal during the experiment. Coal was subjected to time-varying xenon (although not a perfect analog for methane, it provides good contrast under X-rays) gas pressure for the experiment. Adsorbed amounts at different locations were determined by scanning the coal at different times. Qualitative CT images and quantitative image data were used to investigate and compare the regions where gas is transported and stored as well as the rate of adsorption at different regions having different pore structure, and composition. The SEM and CT imaging techniques used in this study enabled us to investigate the coal microstructure falling into macropore range (>1 mum with SEM and 0.3135 mm with CT). This study clearly demonstrates that, for the specific coal sample and xenon gas conditions, different structures (in the length scale given above) and lithotypes have different adsorption capacity and rate behavior. SEM images were also used to define the regions showing different adsorption behavior. (C) 2001 Elsevier Science Ltd. All rights reserved.