A comparative characterization of the structure of normal and abnormal (osteoporotic) human lumbar and thoracic vertebrae samples was carried out to reveal the type of possible disorder. Samples from the bone fragments extracted during the surgery due to vertebra fractures were examined by scanning electron microscopy (SEM), conventional and high resolution transmission electron microscopy (TEM and HRTEM), and X-ray energy dispersive spectroscopy (EDS). Contrary to what might be expected in accordance with possible processes of dissolution, formation and remineralization of hard tissues, no changes in phase composition of mineral part, crystal sizes (length, width, and thickness), and arrangement of crystals on collagen fibers were detected in abnormal bones compared to the normal ones. The following sizes were determined by HRTEM for all bone samples: <= 20 nm in length, 3-15 nm in width, and 0.8 nm in thickness (the height of hexagonal HAP unit cell along the [2 (11) over bar0] direction. Significant overgrowth of organic fibers filled up the former paths for blood vessels and nerves together with organic films covering the mineral part was revealed by SEM only in osteoporotic bones. EDS showed that this organic tissue was not mineralized. Penetration of such organic fibers inside bones can result in bone dilatation and lower the mineral density, deteriorating the mechanical properties and finally terminating in fracture.