Within the MEMENTA-study informal caregivers of grown-up persons with an intellectual disability (ID) with and without a comorbid mental disorder were interviewed. Main outcomes were family burden, quality of life, psychiatric symptomatology and problem behavior. The sample consisted of 123 informal caregivers. Problem behavior was associated with a higher family burden than psychiatric symptomatology. Rather than mental disorders, problem behavior seemed to be more relevant for the experience of family burden.