Background: In most developed countries the prevalence of smoking habits is decreasing in men, while in women the prevalence seems to decline in Northern Europe but to increase in the Mediterranean area. The present research aims at assessing time trends in smoking habits in Italy. Methods: In the frame of the Italian Study on Asthma in Young Adults (ISAYA) a random sample of the Italian population aged 20-45 years was administered a mailed questionnaire in 9 Italian centers between 1998 and 2000. Cumulative response was 72.7% (18873/25969). Kaplan-Meier survival curves and tog-rank test were used to compare probability of remaining a life-time non-smoker across birth cohorts (1953-58, 1959-63, 1964-68, 1969-73, 1974-78). Probability to quit smoking was also evaluated among ever-smokers. Results: Probability to persist as a non-smoker significantly increased across subsequent generations in both sexes. At the age of 20 years this probability amounted to 41.7% (95% CI 39.4-44.0%) in men and 52.7% (50.4-54.9%) in women born between 1953 and 1958, and it increased to 57% (54.8-59.1%) in men and 68.7% (66.6-70.7%) in women born in 1969-73, but no further decline in smoking habits was observed in the next birth cohort (1974-78). Also the probability to quit smoking significantly increased from the 1953-58 birth cohort to the 1969-73 one. Conclusions: Smoking has declined among Italian young adults of both genders. Further efforts are necessary to promote active anti-smoking campaign, especially among adolescents, which are at higher risk of starting to smoke