The solubility of supercritical carbon dioxide (ScCO2) in solid (298 K) and melted (323 K) poly(ethylene glycol) (PEG), in the pressure range (7 to 25) MPa, was measured using a magnetic suspension balance. The phase behavior of the CO2 + PEG system was modeled by using the Sanchez-Lacombe equation of state (EOS) and statistical associating fluid theory (SAFT). The results show a good solubility of CO2 in polymer and a good accuracy of the thermodynamic models in describing the phase equilibrium of the working system. The experimental data are also in good agreement with the solubility values previously described in the literature, obtained by employing different experimental techniques.