Longitudinal studies have reported an association between early childhood lung disease and adult respiratory disease. This issue has not been addressed in the Nordic countries. We studied the association between hospitalization for lung disease in early childhood and asthma in young adulthood in a Norwegian population sample, while estimating the attributable fraction of childhood hospitalization. A population-based survey in Bergen, Norway included a random sample of 4300 subjects aged 20-44 years, of whom 80% responded. The effect of hospitalization for lung disease before the age of 2 years on asthma in adulthood was analysed by logistic and polytomous logistic regressions, adjusting for related variables. Adjusted attributable fractions were estimated from these models. The risk for different measures of asthma was significantly increased in the 103 persons reporting childhood hospitalization (airways symptoms: OR from 1.9 to 2.9; asthma medication: OR = 2.8). The associations with airways symptoms were stronger in women (OR from 2.6 to 5.3) than in men (OR from 1.4 to 2.4). Given a causal association, adjusted attributable fractions showed that childhood lung disease causing hospitalization explained 4% of asthma symptoms. Early childhood hospitalization for lung disease was related to asthma symptoms in young Norwegian adults, more strongly in women than in men. Only a minor proportion of asthma symptoms in this age group could be related to hospitalization for lung disease in early childhood.