ABSTRACT. Objective. To evaluate the quality of life (QOL) of untreated children with newly diagnosed attention-deficit/hyperactivity disorder (ADHD), compared with asthmatic and healthy children.Methods. This prospective, case-control study included a group of 120 children, 6 to 12 years of age, with newly diagnosed ADHD according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Subjects were matched according to age, gender, and health care area with 2 control groups, ie, 93 asthmatic children and 120 healthy children. Sociodemographic characteristics and Child Health Questionnaire scores were collected.Results. The QOL of children with ADHD was rated worse than that of asthmatic or healthy children for most Child Health Questionnaire domains. The greatest differences were found in behavior, social limitations attributable to physical problems, emotional impact on parents, and family activities. Almost every psychosocial domain was more affected in comparison with asthmatic children and both psychosocial and physical domains in comparison with healthy children.Conclusions. ADHD interferes with the daily lives of children, parents, and families even more than asthma, primarily in areas related to psychosocial functioning, although evidence of impaired physical functioning also emerged. Delays in recognition, assessment, and management of ADHD may affect negatively the QOL of those children. ABBREVIATIONS. ADHD, attention-deficit/hyperactivity disorder; CHQ, Child Health Questionnaire; CI, confidence interval; HRQOL, health-related quality of life; QOL, quality of life.A ttention-deficit/hyperactivity disorder (ADHD) is the most common childhood-onset neurobehavioral disorder, and one of the most prevalent chronic health conditions affecting schoolaged children. The prevalence of this disorder among school-aged children is estimated to be between 3% and 12%. 1,2 The disorder is associated frequently with the development of comorbid psychiatric disorders, most commonly oppositional defiant disorder and conduct disorder. 3,4 In addition to social and academic impairment, important reductions in health-related quality of life (HRQOL) have been reported for children with attention and hyperactivity problems. 5,6 HRQOL measures parents' perception of the child's well-being, in terms of physical, mental, and social domains. The concept adopts a patient-centered approach and uses parents' assessments of their child's condition rather than assessments by clinicians or evaluations based on biomedical parameters. 7 This approach focuses on the broader functioning of children and the extent to which parents perceive that disorders interfere with the daily life of children and their families. 8 ADHD is associated with broad impairment in many HRQOL parameters, including academic performance, behavior in school, peer relations, and family functioning. However, the effect of the disorder on everyday functioning and well-being remains largely unexplored in clinical practice. 9 We are aware of 6 st...