To observe and report rates of, and reasons for, parents' refusal to consent to the participation of their children in appropriate clinical research.The parents of children admitted to hospital with a diagnosis of pneumonia or of empyema were asked for informed consent to research involving blood, urine and nasopharyngeal secretion samples from their child. Circumstances and numbers of agreements and refusals were compared and underlying reasons suggested.Of 144 consent requests, ten were refused, which appeared to be linked to: not wanting the child to undergo further tests, lack of interest in participating in studies, research possibly delaying discharge, and anxiety regarding written consent and the length of information sheets.Severity of the child's illness appeared to determine the parent's decision. Involvement and assistance of non-research nursing and medical staff and previous introductions to the researchers are helpful. The timing and setting for the consent process should be selected carefully. Adequate, accessible study information for parents and children contributes to successful recruitment of participants.