An evaluation of the ability of the stretched exponential (SE) equation to describe the sorption kinetics and the rate of expansion/contraction of hard coal in coal-carbon dioxide, coal-methane and coal-CO2/CH4 mixture systems was performed. In order to address this issue the adequate sorption experiments were carried out at high pressure by means of the volumetric method on a cubicoid solid samples. Simultaneously the kinetics of coal sorption-induced swelling were monitored. For two coals under investigation a linear and a non-linear relation between coal expansion and the amount of sorbed gas was observed. The SE equation shows a very good agreement with the sorption experimental data obtained for both coals, it is also able to accurately describe the sorption -induced-swelling of lower rank coal and the CH4-induced swelling of higher rank coal however it does not give a reasonable fit to swelling kinetics induced by sorption of CO2 and CO2\CH4 mixtures on higher rank coal. The highest characteristic rate parameter k was found for CO2 sorption on lower rank coal, the lowest was calculated for CH4 sorption on the same coal and the values of k for higher rank coal are in between. The values of stretching parameter b for higher rank coal are greater than for lower rank coal, i.e. between 0.55 and 0.75 and <0.5, indicating a relatively narrow and a relatively broad distribution of characteristic relaxation times of sorption processes, respectively. Generally, the values of parameters k and b calculated for CO2, CH4 and CO2\CH4 mixture sorption-induced swelling are lower for lower rank coal. The values of parameter b for swelling phenomena are not compatible with these of sorption processes. (C) 2017 Elsevier B.V. All rights reserved.