In liquids and in polymeric membranes, a precise determination of their transport properties is of paramount importance. In this work, an NMR method to measure sequentially the solubility and diffusion coefficients of carbon dioxide in liquids (n-alkanes and 1-alkanols) and in polymer membranes (polyethylene, polybutadiene, and polycarbonate) is described. The results show that NMR measurements are very reproducible and in good agreement with those determined by other methods. Considering that the gas permeability is defined as the product of the solubility and diffusion coefficients, the method allows the determination of all transport parameters in an accurate manner. The influence of chain length, viscosity, and solubility parameters on the transport coefficients of [C-13]O-2 in alkanes and 1-alkanols was also analyzed and compared to those measured in polyethylene.