The objective of this study was to compare psychosocial characteristics of children with asthma and children with bronchial hyperreactivity with those of normal children. A population-based study of 2634 children (mean age, 10 years) was carried out. Pulmonary function tests of children were performed in children before and after cold air hyperventilation challenge to determine bronchial hyperreactivity. Parental assessment of children's behavior was evaluated with 15 questions about school/learning habits, level of activity, communication/affection, and sleeping patterns. A factor analysis was performed and the factor loading adjusted for confounders compared in the different groups. Asthmatic children sleep less well than normal and hyperreactive children (p < 0.001). Unexpectedly, however, all other single items did not differ significantly. As a result of the factorial analysis we obtained two factors. On the first factor, measuring school behavior and learning, there was a small difference between asthmatic and normal children, which could not be found on the second factor indicating activity and communication. We conclude that psychosocial differences of asthmatic children are less remarkable than expected. As a result of the examination of the hyperreactive children it is likely that asthmatic children are influenced more by secondary psychosocial factors than by any primary effect of asthmatic disease.