AIM: To evaluate the prevalence and predictive factors of osteoporosis in patients with gastric adenocarcinoma after gastrectomy.METHODS: The study included 133 patients diagnosed with gastric adenocarcinoma but who did not undergo prior diagnostic work-up for osteoporosis. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) and vertebral deformity was assessed by plain X-rays. We evaluated the effects of age, sex, body mass index (BMI), anemia, back pain,vertebral deformity, tumor staging, reconstruction type,and past medical history to determine predictive factors of osteoporosis in these patients.RESULTS: The prevalence of osteoporosis in the lumbar spine was 38.3% (male, 28.9%; female, 54.0%), and 15.0% in the femoral neck (male, 10.8%; female,22.0%). The vertebral deformity rate was 46.6% (male,43.4%; female, 52.0%). Age, BMI and hemoglobin correlated with BMD (P ＜ 0.01). In males, anemia and age ＞ 64 years were independent predictive factors of osteoporosis in multivariate analysis. In females, back pain was an independent factor for osteoporosis.CONCLUSION: The results of this study revealed that prevalence of osteoporosis and vertebral bone deformity rate were high in gastric cancer patients, regardless of post-gastrectomy duration and operation type. Early diagnosis and a proper management plan must be established in these patients.