There is an increased focus on, and evidence of, children's capability to both understand and make decisions about issues relating to participation in medical research. At the same time there are divergent ideas of when, how and to what extent children should be allowed to decide for themselves. Furthermore, little is known about parents' views on these matters, an important issue since they often provide the formal consent. In this questionnaire study of 2500 families in south-east Sweden we explored parents' (...) views on issues relating to information, consent and research data. We found that parents are generally positive about supplying their child with individual information and assuring the child's consent/assent to participation. However, parents' views vary regarding the extent to which children should influence research data: as many as 47–61% of our sample were opposed to children's rights to decide about the use and storage of biological samples and natural history data. Parents who are opposed to child consent and a wider influence on their research participation argue that parental authority and research quality are two important factors opposing enhanced child influence. Drawing on this, we underline the need to discuss how to balance children's rights against parental autonomy and research interests before implementing any standardized protocols granting children the right to consent and revoke data in long-term research. (shrink)