Capillary invasion-type models such as molecular sorption theory [Vesely D. Polymer 2001; 42:4417-22] and Bosanquet equation are applied to the diffusion of fluid/solvent into glassy polymers. It is found that both models show close description of the Fickian and Case II diffusion rates in agreement with the available experimental data. The Case II diffusion linear front advance, however, can be interpreted more naturally as inertial effect in the frame of the Bosanquet model. It is also shown that there is a connection between the Bosanquet model and 1D correlated random walk with the probability density described by the telegraph equation. The telegraph equation can be used to estimate the concentration profiles of the penetrating fluid. (C) 2013 Elsevier Ltd. All rights reserved.