Introduction: Progress in diagnosis and treatment of patients with intoxication-type inborn errors of metabolism (IT-IEM) such as urea cycle disorders, organic acidurias or maple syrup urine disease is resulting in a growing number of long-term survivors. Consequently, health-related quality of life (HrQoL) of patients is increasingly regarded as a meaningful outcome parameter. To develop the first validated, disease-specific HrQoL questionnaire for IT-IEM, patients and parents were interviewed as content experts to identify major physical and psychosocial constraints and resources. Methods: Focus group interviews with 19 paediatric IT-IEM patients and 26 parents were conducted in four metabolic centres in Austria, Germany and Switzerland. Disease-specific HrQoL categories were established by qualitative content analysis. Results: Fourteen disease-specific topics related to the three well-established generic HrQoL dimensions of physical, mental and social functioning were derived from the interview transcripts. Both patients and parents perceived dietary restrictions and social stigmatisation as major burdens. Dietary restrictions and emotional burdens were more important for young (