The solubility of carbon dioxide (CO2) and dimethyl ether (DME) blends in polystyrene (PS) is studied as a function of the temperature and the pressure. The solubility was measured by means of the gravimetric method and a visualizing dilatometer which determined the swollen volume to compensate for the buoyancy change due to swelling. The solubility of the blend gases for the ternary PS/CO2/DME system is also predicted by the Simha-Somcynsky (SS) equation of state (EOS). The theoretical prediction of the blend solubility was in agreement with the experimental results. Adding DME to PS not only decreased the pressure required to dissolve CO2 in PS but the effects of plasticization were also observed. The remarkable plasticization effect due to the presence of DME increased the CO2 solubility via an increased free volume of PS. (C) 2016 Elsevier Ltd. All rights reserved.