Background: Knowledge about assent or dissent of children to non-therapeutic research is poor.Objectives: To assess sociodemographic characteristics in healthy children and adolescents who were invited to participate in non-therapeutic research, to evaluate their motives for assent or dissent and their understanding of the information given.Methods: A total of 1281 healthy children and adolescents six to sixteen years of age were invited to participate in a non-therapeutic study and a questionnaire.Results: Assenting children were motivated by a desire to help sick children (...) and to gain experience with participating in a research study . Dissenting children made their decision because of worries about having a blood or a urine sample taken or because of worries about a doctor’s examination . Fewer children in the assent group than in the dissent group worried about the doctor’s examination . In the assent and dissent group, 568 and 343 children, respectively, said they were able to understand some or all of the written information , and 650 and 330 , respectively, were able to understand some or all of the verbal information .Conclusions: Sociodemographic characteristics may not influence healthy children’s decision to volunteer for non-therapeutic research. Assenting children have altruistic and educational motives, whereas worries about procedures may cause children to dissent. A great majority of school children and adolescents feel capable of understanding and giving assent or dissent to non-therapeutic research. (shrink)