PURPOSE: To draw up a clinical portrait of children with cerebral palsy (CP) in relation to their postural stability in the sitting position, by means of questionnaires addressed to their parents and clinicians and to identify the parameters related to body geometry, activities of daily living (ADL) and the period of the day that are linked with their postural instability. METHOD: Parents and therapists of 31 children with CP (17 boys, 14 girls; mean age, 12.7 years; age range, 8-18 years) took part in the study. As a first step, four questionnaires were developed by the research team. Nine clinicians were then involved in a focus group to validate their content. They were thereafter sent to the parents and therapists of the children. Descriptive analyses (percentage) were performed on the results of the questionnaires. RESULTS: A high percentage of instability was reported by both children’s clinicians and parents (81% and 70%, respectively). This instability mainly occurred after less than half an hour in the wheelchair. Sliding and posterior pelvic tilt, pelvic obliquity and pelvic rotation were identified as the main problems of instability encountered by these children. CONCLUSION: The children involved in this study experienced some difficulties in achieving various ADL, because of their instability in the seated position. As the maintenance of postural stability is essential to the performance of most motor acts, it is essential to better understand the parameters associated with postural instability of children with CP in the seated posture.