Background/Aim: Several risk factors have been suggested for osteoporosis which frequently occurs in inflammatory bowel disease (IBD) patients. We studied prevalence and risk factors for reduced bone mineral density (BMD) in IBD patients at the University Hospital of Zürich, Switzerland. Methods: The BMD was determined by dual-energy X-ray absorptiometry at the lumbar spine and femoral neck in 88 IBD patients (55 with Crohn’s disease, 30 with ulcerative colitis, and 3 with indeterminate colitis). Z scores were obtained by comparison with age- and sex-matched normal values, and T scores by comparison with sex-matched healthy young adults. Osteopenia and osteoporosis were defined according to the WHO guidelines. Predictive factors for BMD were analyzed by group comparison and stepwise regression analysis. Results: Osteopenia was present in 43% of the patients at the lumbar spine and in 42% of them at the femoral neck. Osteoporosis was present in 14% of the patients at the lumbar spine and in 5% of them at the femoral neck. At the lumbar spine, stepwise regression analysis showed that body mass index, age, number of bowel resections, topic steroids, and azathioprine correlated with the Z scores. Cumulative steroid dose, topic steroids, age and bowel resection were found to be predictors for a pathological T score. At the femoral neck, regression analysis showed that body mass index, age, topic steroids, and azathioprine correlated with the Z scores. Only a low body mass index was a significant predictor for pathological femoral T scores. Conclusions: Osteopenia and osteoporosis are commonly found in IBD patients. Steroid treatment and bowel resection were significant risk factors for osteoporosis of the lumbar spine. However, disease-inherent factors also appear to confer a major risk, indicating that the BMD should be determined in all IBD patients, irrespective of steroid treatment.