We extend a previously published compressible lattice model to the prediction of glass-transition temperatures in CO2 + polymer systems. We have applied the model to published data as well as to new measurements of glass-transition temperatures in CO2 + poly(methyl methacrylate) (PMMA) and CO2 + poly(lactic acid) (PLA) systems. We demonstrate that the model is able to predict glass-transition temperatures in CO2 + polymer systems using a parameter that is obtained from sorption data and a second parameter that is obtained from FTIR measurements. The parameters are not dependent on temperature, pressure, or polymer molecular weight.