Cortical and trabecular bones were modeled as nanocomposite materials with hierarchical structures spanning from collagen-mineral level to cortical and trabecular bone levels. In order to verify theoretical models, compression testing was done on cortical and trabecular bovine femur bone samples and the experimental data were compared with the theoretical results. The micro-computed tomography technique was used to characterize the porosities and structures of these bones at different length scales and to provide the inputs needed for the modeling. To obtain more insight on the structure of bone, especially on the interaction of the main constituents (collagen and mineral phases), both cortical and trabecular bone samples were deproteinized and demineralized and, afterwards, tested in compression. This information was used to fine-tune our multi-scale model representing bone as an interpenetrating composite material. Very good agreement was found between the theory and experiments for the elastic moduli of untreated, deproteinized, and demineralized cortical and trabecular bones.