Polymers and polymeric composites have been well known to absorb and retain moisture in wet and humid environment, resulting in severe degradation of optical, electrical and thermo-mechanical properties. To describe the degree of property loss, moisture absorption by polymers and polymer composites have been often investigated using diffusion-based models. Although it has been common practice to use a one-dimensional Fickian model to characterize and predict the moisture absorption, most polymers and polymeric composites exhibit non-Fickian absorption behavior, primarily due to the water-polymer affinity. In addition, the presence of fibers, nanomaterials, and defects such as voids and microcracks, as well as micro- and nanostructural features, such as process-induced dispersion considerably affect the moisture absorption behavior. In this article, a comprehensive hindered diffusion model is utilized to fully characterize the moisture absorption in thermosetting polymers, micro- and nanocomposites, and multilayered laminates. The model is developed to account for various types of Fickian and non-Fickian absorption behavior, as well as capturing the edge effects, process-induced anisotropy, and moisture storage by the voids and at reinforcement/matrix interfaces. Predictive capabilities of hindered diffusion model is presented for a number of realistic cases ranging from neat epoxy resins to glass/epoxy laminates and nanoclay composites to highly porous polymer foams. Keywords: Moisture Absorption, Anisotropy, Concentration Profiles, Hindrance Effects, Voids.