In this work we investigate the effect induced by a cavity on the moisture diffusion behavior of a polymer matrix. Diffusion at the interface between the matrix and cavity is modeled owing to a thermodynamic approach. In this study, the effects related to crack shape and volume fraction on the overall diffusive behavior are accounted for. Two cases were treated: the case where the cavity is closed and located within the bulk of the matrix volume and another one where the cavity corresponds to an open crack. Two parameters were chosen for modeling the cavity: its geometric configuration and its volume fraction. In the case of a crack contained in the bulk of the material, several numerical examples have been performed for either a single cavity or for several cavities. In this second case, the effects related to the spatial dispersion of these cavities were investigated. The identification results for the diffusion coefficient show an increased sensitivity to the presence of damage in the form of cracks, especially when these cracks tend towards a flattened shape. In addition, a remarkable diffusion anisotropy takes place.