IntroductionTo evaluate the effect of telling undergraduate smokers their lung ages on the rate of smoking cessation.MethodsThis randomized controlled study involved 142 eligible volunteer current undergraduate smokers. They were randomly allocated to the study group (group 1; <i>n</i> = 72) and the control group (group 2; <i>n</i> = 70). Participants in group 1 were told their lung age, received a 5-minute motivational interview, and were given raw figures of their pulmonary function, while participants in group 2 received the same intervention except the lung age. Initially (evaluation 1), the subjects’ lung ages were estimated through spirometric assessment of forced expiratory volume in 1 second. The number of smoked cigarettes per day was reported and the smoking status was ensured through the assessment of exhaled carbon monoxide at evaluation 1, after 6 months (evaluation 2), and after 12 months (evaluation 3).ResultsAt evaluation 2, the overall follow-up rate was 95.07%. There was a significant difference in the smoking quit rate between group 1 (23.61%) and group 2 (10%) (<i>p</i> = 0.03). At evaluation 3, no change existed in the follow-up rate. The smoking quit rate was 19.4% and 4.3% for groups 1 and 2, respectively (<i>p</i> = 0.01).ConclusionsTelling undergraduate smokers their lung ages can significantly improve the smoking quit rate in a short- and long-term perspective. The long-term partial relapse status arouses the question about other contributing factors out of the scope of this study.