The psychiatric morbidity in a group of 36 patients with cystic fibrosis (CF) was compared with that in a healthy matched control group. Psychiatric diagnoses, based on the ICD scheme of classification, were much more common in the CF group. Social background factors were related only poorly to psychosocial adaptation. There were moderate correlations between impaired pulmonary function and increased psychopathology; stronger correlations were found with variables related to mental health of the parents and family life. It is suggested that many children with CF require psychological help, a need that may increase as the disease progresses.