We examined associations between child symptoms, demographic variables, parent and family characteristics in a long-term follow-up study of 214 outpatient children with attention-deficit/hyperactivity disorder (ADHD). The children’s mean age was 12.6 (SD = 2.1) years, and the mean interval from diagnosis to follow-up was 3.7 (SD = 2.2) years. We compared the characteristics of the clinical group with a community group (n = 110) recruited from the same catchment area. Parents filled out questionnaires on child symptoms, parent characteristics, and family functioning. The results showed that parents of young boys (<13 years) experienced more parenting stressors than those of adolescent boys (>=13 years), but the opposite was true for parents of girls. Parents of children with both ADHD and oppositional defiant disorder symptoms in the clinical range experienced significantly more parent and family dysfunctions than those of children with ADHD only (even after controlling for levels of ADHD symptoms in the child). Parents of children in the community group experienced significantly less parent and family dysfunctions than those of children with ADHD. Partial correlations between parent characteristics and child symptoms showed that oppositional symptoms were most strongly associated with parent and family dysfunction. Fathers experienced significantly less parenting stress, parental efficacy, and child involvement than mothers. We conclude that parents of children with ADHD experienced considerable strain related to a broad range of parent and family characteristics. Assessment of such characteristics should be part of routine assessment procedures and a prerequisite for family-focused treatment of children with ADHD.