The views of over 200 children (11-16 years old, who were either healthy or attending paediatric medical clinics with a chronic illness) on issues relating to paediatric clinical trials were determined by a questionnaire. Children with a chronic illness had a better understanding of the concept of dosing of medicines (40% vs 23%) and placebo (34% vs 20%). They were more likely to support children's involvement in clinical trials (51% vs 37%). The altruistic nature of children in both groups was similar. It was of concern, however, that 57-63% children would participate as healthy volunteers in a cancer drug trial. Both groups were able to differentiate between the different types of illnesses where it is appropriate to study medicines in children (86-89% for illness where there is no treatment; 34-40% for 'me-too' drugs). Young people should be given more opportunities to be involved in decision-making regarding clinical trials of medicines.