Opportunistic use of computed tomography (CT) allows assessment of bone status from studies obtained for other purposes. The linear x-ray attenuation coefficient is known as the Hounsfield unit (HU). HU values can be determined for any region of interest using standard imaging software. HU values strongly correlate with bone mineral density. A threshold of <135 HU for the L1 vertebral body indicates a risk for osteoporosis. HU values have been used to assess other bone regions, including the wrist, proximal and distal end of the femur, and sacrum, to predict future fracture and the presence of osteoporosis. Opportunistic use of CT aids in the identification of patients who are not otherwise suspected to be at risk for osteoporosis.