- To study the impact of mild to moderate asthma on smoking habits in adolescents. Specifically, we tested the hypothesis that asthma does not prevent adolescents from smoking. A research questionnaire, filled by a systematic sample of military personnel upon enrolment to service in the Israeli Defense Force (IDF), was analyzed. Conscripts were asked to voluntarily fill (after obtaining a signed informed consent) a research questionnaire about their medical history, and several health related topics including smoking. This database was matched with the military medical profile of the soldier, which includes the patient asthma status. Overall, 38,047 young adults were included in this study. There was a significant increase in the rate of mild to moderate asthma, from the mid-1980's to date. During the 1980's and early 1990's, asthmatics smoked significantly less frequently (20–22%) than non-asthmatics (25–27%). In the mid- to late-1990's, the smoking rates increased relatively more in asthmatics, to the point that in the last 8 years of this study, they were found to be almost identical in both groups, at a rate of approximately 30%. The presence of asthma is not a powerful motivating agent to prevent from smoking. It is likely that smoking asthmatic teenagers are at risk for suboptimal lung growth, and as young adults, they will become at greater risk of lung function deterioration. We suggest that primary care physicians, caring for asthma in children, adolescents, and young adults, should explain the particular risks generated by tobacco smoking. © 2004 Wiley-Liss, Inc.