BACKGROUND: Although, adiponectin might be associated with bone metabolism, the relationships between serum adiponectin and bone mineral density (BMD) as well as vertebral fracture in type 2 diabetes are still unclear. OBJECTIVE AND METHODS: We investigated the relationships between each of serum total and high molecular weight (HMW) adiponectin versus BMD, bone markers, and the presence of vertebral fractures in a total of 231 men and 170 post-menopausal women with type 2 diabetes. RESULTS: Multiple regression analysis adjusted for age, duration of diabetes, BMI, serum creatinine, and HbA(1c) showed that serum total adiponectin was negatively correlated with BMD at the total, lumbar spine, and femoral neck (r=-0.165, P<0.05; r=-0.187, P<0.05; and r=-0.136, P<0.05 respectively) and positively with urinary N-terminal cross-linked telopeptide of type-I collagen in men (r=0.148, P<0.05), and that serum HMW adiponectin was negatively correlated with BMD at the lumbar spine (r=-0.146, P<0.05). Multivariate logistic regression analysis adjusted for the parameters described above showed that total adiponectin was associated with the presence of vertebral fractures in men (odds ratio (OR)=1.396, 95% confidential interval (CI) 1.020-1.911 per s.d. increase, P<0.05), and both total and HMW adiponectin were associated with moderate or severe vertebral fractures (OR=1.709, 95% CI 1.048-2.787 per s.d. increase, P<0.05 and OR=1.810, 95% CI 1.112-2.946 per s.d. increase, P<0.05 respectively), but not in post-menopausal women. CONCLUSIONS: Serum adiponectin could be associated with BMD and turnover and clinically useful for assessing the risk of vertebral fractures in type 2 diabetic men.