Susceptibility of polymeric composites to moisture absorption and the resulting degradation of properties have been well known for several decades. Most moisture absorption models for composites assume a simple, diffusion-based, reversible process, often referred to as the Fickian model. These diffusion-only models do not account for the interfacial moisture storage at the fiber-matrix interface or possible molecular binding between the water and the polymer. However, in several high-performance and mission critical applications, more comprehensive models accounting for the edge effects, anisotropy of absorption, molecular interactions, and interfacial storage are required to fully describe the short- as well as the long-term moisture absorption dynamics. In this presentation, a more comprehensive moisture absorption model that combines the diffusion hindrance due to molecular bonding, three-dimensional anisotropy, and interfacial moisture storage will be presented. The developed model uses two additional phenomenological parameters that can be related to the actual micro or nanostructure of the composite. In addition, the hindered diffusion/storage model can fully explain the transport of moisture into closed cell synthetic foams, lightweight sandwich structures, and multi-layered laminates with or without process-induced voids. Experimental findings support this theoretical framework which is validated by composite systems containing various types of nanoclay or other additives such as micro glass spheres loaded at different volume fractions.