Quality of life (QoL) in children and adolescents with bleeding disorders and their families is a relatively new topic. It is important to understand more about QoL in this patient population to evaluate and if necessary to improve the care patients receive. To achieve this aim, a questionnaire to assess patients' QoL in hemophilia was developed and psychometrically tested. Three hundred twenty hemophiliac children and adolescents from six European countries and their families were asked to fill out a questionnaire regarding different aspects of their well-being and functioning, as well as their views on hemophilia care. Generic QoL questionnaires showed that children with hemophilia have a higher QoL than other patients with chronic disease, such as asthma/atopic dermatitis and obesity. Several determinants affected patients' QoL (e.g., number of bleeds, social support). Parents' and children's assessments differed with regard to social and emotional aspects of QoL. The study showed that variations in QoL can be explained by clinical and psychosocial factors and suggested that QoL can be assessed and enhanced both by medical and non-medical (e.g., psychological) interventions.