The contribution of non-cylindrical pores within the coal has been determined by means of mercury porosimetry using a subsequent compression-decompression procedure. Experiments have shown that about 40% of the total particle porous volume cannot be described by cylindrical pores, forming vesicles. On the assumption that these vesicles are of spherical shape, it has been found that most probably they are situated at the intersections of the cylindrical pores of the same size range. A modification of the random pore model (RPM) by Gavallas and Wilks has been proposed (RPM-SC) enabling the spherical vesicles to be incorporated.