The amount of unburned organic matter in solid residues from coal combustion process is one of the indicators of the process and may influence their usage as by products. During the examination of slag and fly ash from Bedzin Power Station (Poland) the following forms of unburned coal were distinguished: crassispheres, tenuispheres, isotropic and anisotropic networks, tenuinetworks, honeycombs, inertinite and detritus. Slag characterises higher crassispheres and networks contents while high detritus contents are typical of fly ash. Spheres content in both slag and fly ash is always lower than vitrinite content in the feed coal. Fusinite content in the feed coal is lower than inertinite content in the solid residues. Other inertinite macerals probably participated in the formation of honeycombs. (C) 2002 Elsevier Science Ltd. All rights reserved.