BACKGROUND: Lung age, calculated from sex, forced expiratory volume in one second (FEV1), and height, was developed to illustrate premature changes to the lungs and could be used to motivate smoking cessation. However, this method has not been tested in association with smoking in Korea. The purpose of this study was to investigate the association of lung age with smoking and other factors in Korean males. METHODS: We reviewed the records of 1,100 healthy men who visited a health promotion center at Ewha Womans University Medical Center from January 2008 to June 2009. Lung age was calculated from FEV1 and normal predictive values of spirometry according to age in the Korean population. The difference between lung age and chronological age was evaluated in relation to smoking status, weight, body mass index, waist, muscle mass, fat mass, and exercise. RESULTS: The age difference was significantly higher in current smokers than in non-smokers (12.47 +/- 19.90 vs. 7.30 +/- 19.52, P < 0.001). Additionally, the age difference was positively correlated with life time pack-year (beta = 0.223; P < 0.001) and fat mass (beta = 0.462; P < 0.001). Lung age increased 1 year for 4.48 pack-year increase or for 2.16% increase in fat mass. CONCLUSION: We found a significant relationship between lung age and both smoking status and fat mass in healthy Korean males. Lung age may be a useful tool for motivating cessation of cigarette smoking and management of risk factors related to obesity.