['Case controlled study.', 'To explore the relative effects of body mass index (BMI) and the presence or absence of adolescent idiopathic scoliosis (AIS) on bone mineral density (BMD) as evidenced by Z-scores in adolescents.', 'Prior studies have identified adolescents with idiopathic scoliosis as having "osteoporosis" or "osteopenia," when only a small percentage of subjects in these studies actually had bone density that was clinically abnormal. The terms osteoporosis and osteopenia as used in adults cannot be applied to adolescents and children, as fracture risk has not been well correlated to Z-scores. As we had noted that our scoliosis patients of normal and heavy weight had normal Z-scores, this study was undertaken to explore the relationship of bone mineral density to body mass index in adolescents with and without scoliosis.', 'Dual energy x-ray absorptiometry (DXA) scans of 49 adolescents with adolescent idiopathic scoliosis were compared to 40 normal control adolescents. Z-scores were compared to reduce variability when comparing subjects of varying age and genders. Student t test or simple linear regression was used to explore relationships between Z-scores and clinical and demographic variables.', 'In both groups of subjects, Z-score was most strongly correlated with BMI (P < 0.001). The presence of scoliosis had the effect of lowering the Z-score as if the individual had "lost" 3.4 BMI units.'] Are adolescents with idiopathic scoliosis osteoporotic?