A comparative investigation of the composition and the morphology of char particles was conducted: char particles were recovered from fly ashes of two power stations in Russia from burning of high- and low-reactivity high-ash coals; the known results of studies of char particles generated in laboratory conditions from coals characterized according to the ASTM D388-98a standard were also used. The composition of organic and mineral components of different fraction char particles was studied. An inverse correlation between the content of the organic substance and the iron content in char particles was identified. The morphology of the char particles for the three main types (Cenospheric, Network and Solid) and the influence of coal reactivity and temperature on char morphology were investigated. The morphology of the mineral component of char particles of the two varieties of coals was also studied. It was shown that the high-temperature of industrial burning of Ekibastuz coal results in melting of the mineral substance and forming of micron-scale microspheres located in the lamellar porous structure of the carbon matrix. (C) 2007 Elsevier Ltd. All rights reserved.