This study compares the reproducibility, construct validity and responsiveness of self-report and parent-report quality of life questionnaires How Are You (HAY) for 8–12-year-old children with asthma. A total of 228 Dutch children with asthma and their parents completed the HAY and daily recorded the child's asthma symptoms in a diary. Additionally 296 age- and -gender matched healthy children and their parents completed the generic part of the HAY. Reproducibility and responsiveness were examined in a sub-group of 80 children with asthma. In this group, three measurements were carried out, at baseline, after one week and once during the following 6 month when the clinical asthma status had changed. The within-subject standard deviations (SD) of three dimensions (physical activities, social activities, self-management) differed significantly (p < 0.05) in favour of the parent-version, indicating that the reproducibility of the parent version was better than that of the child version. The mean score-differences between children with asthma and healthy children as reported by parents did not significantly differ from those reported by children, except for cognitive activities (e.g. be able to concentrate on school work). The mean differences with regard to children with a different actual asthma status (symptom analysis), as reported by both informants, did not differ. Compared to the child-version, the parent-version showed greater ability to detect changes in children's quality of life over time for all but one dimension, indicating better responsiveness. The results indicate that in discriminative studies child and parents reports can be substituted on a group-level. In longitudinal studies data have to be obtained from parents. Consequently, caregivers collecting quality of life data for longitudinal purposes in daily practice should collect these data simply from parents.