The sorption of supercritical carbon dioxide (CO2) onto the glassy polymers poly(methyl methacrylate) (PMMA) and polystyrene (PS), under relatively high pressures and temperatures, was investigated. Two experimental methods were used: the quartz crystal microbalance (QCM) and the mass-loss analysis (MLA) after CO2/Polymer contact in a high pressure cell. Whenever possible, the sorption isotherms were compared with the corresponding ones from the literature. Our measurements prove, in particular, the complementary character of the QCM and MLA methods and the usefulness of QCM for the low pressure measurements and of MLA for the corresponding measurements at high pressures. The interesting phenomenon of sorption-induced glass transition was also monitored. The Non-Random Hydrogen-Bonding (NRHB) model of mixtures of fluids was used to describe the sorption-induced glass transition temperature by applying it to, both, the glassy and the rubbery state. The same model was used to correlate the sorption data at all investigated conditions. (c) 2005 Elsevier B.V. All rights reserved.