Objective: Increasing rates of survival have raised the question of medical and psychosocial factors contributing to quality of life of patients with congenital cardiac disease. We investigated the impact of the severity of disease, and social disadvantage, on the quality of life of patients and their primary caregivers. Methods: One hundred and thirty two families participated in a computer-assisted evaluation of their quality of life in a German outpatient centre for paediatric cardiac diseases. Quality of life for the patients was evaluated by a multi-dimensional proxy-measure. The quality of life of the caregivers was evaluated by a multi-dimensional self-reporting measure. Severity of the disease was evaluated by the responsible paediatrician. Social disadvantage was defined as single-parent status, ethnic minority status, unfinished parental education or professional training, and/or unemployment. Analyses of variance were calculated with mild, moderate, or severe forms of disease, and risk as opposed to no risk for social status, both factors being treated independently, and the quality of life of the patients and their caregivers as dependent variables. Results: We demonstrated significant effects of the severity of disease on the quality of life of the children, and of social disadvantage on the quality of life of both the children and their parents. A significant interactive effect indicated a cumulative negative impact of the severity of the disease and social disadvantage on the quality of life of the patients. Conclusion: Programmes providing psychosocial support for children with cardiac disease and their caregivers should consider risk factors which are both medical and social.