The effect of semicrystallinity on the sorption and swelling behavior of polymers in supcrcritical CO2 is investigated. In particular, the experimental behavior measured for four different polymers in a previous work, i.e., poly(methyl methacrylate), poly(vinylidene fluoride), poly(tetrafluoroethylene), and the copolymer tetrafluoroethylene-perfluoromethylvinyl ether, is modeled using four different thermodynamic approaches: the Sanchez-Lacombe method in its nonequilibrium and equilibrium version, a modification of the latter for cross-linked polymers, and the statistical association fluid theory (SAFT) approach. The four considered polymers have an increasing crystallinity from 0% (poly(methyl methacrylate)) to about 50% (poly(vinylidene fluoride)). The results in terms of sorption and swelling are compared and the parameter evaluation procedure is discussed. It is observed that the nonequilibrium Sanchez-Lacombe method performs better than the others in describing the semicrystalline polymers at least from a qualitative point of view. This supports the interpretation that semicrystallinity induces a nonequilibrium effect, since the polymer structure, made more rigid from the presence of the crystallites, does not recover the original compactness after sorption Of CO2.