To explore the role of psychosocial factors in the development and persistence of idiopathic musculoskeletal pain (IMP) in children, 23 children with IMP and 52 children with juvenile chronic arthritis (JCA) were compared at first admission to hospital and at 9 y follow-up. Semistructured interviews were performed at both assessments. At first admission, the prevalence of psychiatric diagnoses was high both in patients with IMP and patients with JCA, but patients with IMP more often had pain models, reported more school stress and more often lived with one biological parent. At follow-up, overall psychosocial functioning and level of chronic family difficulties were improved in both groups, but patients with IMP had a higher prevalence of psychiatric diagnoses and more chronic family difficulties and life events than patients with JCA. The persistence of IMP at follow-up was related to pain models, school stress, less parental education and more chronic family difficulties at first admission. Findings support the association between psychosocial factors and childhood IMP.