A method of visual validation of a widely used dual-mode model for sorption of gases in glassy polymers is presented. Instead of directly fitting the model equation to the sorption data to determine its three parameters, the method evaluates one of the parameters, Henry＇s law coefficient independently and then plot the data in a Linear way. Good linearity was obtained from such plots for the sorption data of CO2 in polycarbonate and polysulfone, which indicated the validity of the assumed model. Moreover, parameter values determined accordingly were seen to be reasonable and self-consistent. Applications of the method were also illustrated for detecting deviations from the dual-mode sorption. Finally, a normalized linear plot is discussed by which sorption isotherms obeying the dual-mode model could be transformed to parallel lines and be specified by a dimensionless parameter.