Fourier transform infrared (FT-IR) spectroscopy was used to reveal weak intermolecular interactions between carbon dioxide (CO2) and the carbonyl groups of several polymers. This interaction affects the solubility of CO2. The polymers used in this study were poly(l-lactide) (PLLA), poly(d,l-lactide) (PDLLA) and poly (ε-caprolactone) (PCL). In the presence of CO2, the wavenumber of the carbonyl groups shifted to a higher value and in the bending mode region of CO2 a new absorption band appeared. For PCL, the effect of CO2 dissolution on the melting point depression could clearly be observed, even at low pressures.