Osteoporosis is a common metabolic bone disorder that may be broadly subdivided into generalized or regional osteoporosis. This article reviews the common causes of generalized osteoporosis with emphasis on the radiological appearances, complications, and differential diagnosis. The more important causes of regional osteoporosis such as disuse osteoporosis, reflex sympathetic dystrophy, and transient regional osteoporosis are also discussed, and their imaging features are reviewed.