This paper deals with ethical issues of particular relevance to longitudinal research involving children. First some general problems concerning information and lack of understanding are discussed. Thereafter focus is shifted to issues concerning information and consent procedures in studies that include young children growing up to become autonomous persons while the project still runs. Some of the questions raised are: When is it right to include children in longitudinal studies? Is an approval from the child needed? How should information to (...) children be handled? A general point stressed is that autonomy considerations underline the importance of adjusting the information given to meet demands. A “presumption of competence” may be needed in research involving children, in order to pay their views sufficient attention. (shrink)