In vivo quantitative techniques for assessing the microstructure of trabecular bone noninvasively and non-destructively include high-resolution CT and magnetic resonance (MR). Compared with MR imaging, CT-based techniques have the advantage of directly visualizing the bone in the axial skeleton, with high spatial resolution, but the disadvantage of delivering a considerable radiation dose. The evaluation of microstructure is useful to investigate the biomechanical property, and to assess the efficacy of anti-osteoporotic agents. Recently, cortical microstructure has been recognized important in relation to biomechanics. Further progress in bone imaging technology is promising to bring new aspects of bone structure in the every day clinical setting.