OBJECTIVE: To investigate the relationship between smoking and bone mineral density in the femoral neck and lumbar spine by measuring urinary cotinine concentrations BACKGROUND: Low bone mass is a major cause of spine and femoral neck fractures in the elderly. There is a limited amount of literature on risk factors for low bone mass in the population (especially in men). Methods: Data from 770 men over 30 years of age, which were obtained from the 5th Korean National Health and Nutrition Examination Cross-sectional Study, were analyzed by t-test, variables were analyzed, and multiple linear regression analysis was done. Results: The bone density of the femoral neck decreased significantly with age, with T values of -0.08, -0.63, and -1.49 in the 30-40, 50-69, and 70-95 year old groups, respectively (P<0.001). The same trend was observed for BMD of the lumbar spine. While education level and income were associated with femoral neck t-values (P<0.001 for the former and P = 0.021 for the latter), only education level was associated with lumbar spine T-values (P = 0.034). Urinary cotinine levels above 10 μg/mL group (active and passive smokers) had lower femoral neck T values compared to cotinine levels below 0 μg/mL group (-0.43 ± 0.98 in the former and -0.33 ± 0.89 in the latter) ( P = 0.114). Multiple linear regression analysis showed that age, urinary cotinine level, body mass index and lumbar spine and femoral neck T-values were significantly associated. CONCLUSIONS: Our study suggests that active and passive smoking and low body mass index have a negative effect on bone mineral density in the femoral neck and lumbar spine.