The transport coefficient of cyclohexane vapor in an activated gamma alumina pellet, estimated using the transient response method on a thermogravimetric analyzer (TGA), is reported as a function of relative saturation. An extended hydrodynamic model is proposed to account for the combined surface and viscous flows in coexisting adsorbed and capillary condensed phases, respectively, in a porous solid with a distribution of pore sizes. The structural features reflected in the isotherm data, as well as in the concentration dependence of the overall diffusivity, are well represented by the proposed model. The results are compared with the earlier hydrodynamic model. The model is also applied to published data, and anomalous trends reported in the literature are discussed.