To mitigate the adverse effects of greenhouse gases on global climate, several options have been proposed. One of the main options is to reduce gas emissions by the storage of CO2 in deep underground formations. Coal seams are of interest owing to their naturally stored methane which can be produced during sequestration and thereby partially offset the costs. However, there are some concerns about the practicality of using coal seams for carbon dioxide storage due to insufficient understanding of the associated physical and chemical processes. In order to develop an efficient strategy for coal seam sequestration, variables that affect the transport and mechanical properties need to be investigated. In this paper the results of a series of experimental investigations are reported, which have been conducted to enhance our understanding of the effects of CO2 adsorption on the mechanical properties of coal. The experimental results show that the adsorption of CO2 changes the elastic modulus and the strength of coal samples, and that these effects are reversible. Simple models are described that have been developed to represent the adsorption-induced changes on the mechanical properties of coal. SEM images suggest that the coal microstructure may also change in the presence of CO2. The adsorption-induced changes in the elastic modulus, strength, and microstructure of coal are believed to be similar to the effects of plasticisers on polymers. (C) 2014 Elsevier B.V. All rights reserved.