OBJECTIVES. The purpose of this work was to examine changes in quality of life, disease-specific functioning, and psychosocial competencies of children and adolescents (8-16 years of age) with anorectal malformations or Hirschsprung disease and to identify predictors of change in quality of life by testing an explanatory model in which background variables explained changes in quality of life via changes in disease-specific functioning and psychosocial competencies. METHODS. Questionnaires were administered to 129 patients with anorectal malformations and 121 patients with Hirschsprung disease within a 3-year interval. Clinical and sociodemographic background variables were measured on the first occasion. Quality of life (physical and mental), disease-specific functioning (defecation-related), and psychosocial competencies (self-esteem, athletic competencies, and school attitude) were measured on both occasions. RESULTS. Patients improved in disease-specific functioning and mental quality of life. Changes in quality of life were indeed explained by the explanatory model. Among other things, the results indicated that patients with a severe form of the disease or with additional congenital diseases showed worsening of school attitude, which in turn affected change in mental quality of life negatively. CONCLUSIONS. Children and adolescents with anorectal malformations or Hirschsprung disease reported better quality of life over time. To improve and maintain an optimal level of children's and adolescents' quality of life, it is important to direct treatment both to reducing symptoms and enhancing psychosocial competencies, in particular by paying attention to school attitude.