BACKGROUND: Attention-deficit hyperactivity disorder (ADHD) is recognised as a common, disabling condition. Little information is available regarding the long-term outcomes for individuals with ADHD in the UK. AIMS: To examine the 5-year outcome for a UK cohort of children with diagnosed, treated ADHD and identify whether maternal and social factors predict key outcomes. METHOD: One hundred and twenty-six school-aged children (mean age 9.4 years, s.d. = 1.7) diagnosed with ADHD were reassessed 5 years later during adolescence (mean age 14.5 years, s.d. = 1.7) for ADHD, conduct disorder and other antisocial behaviours. RESULTS: Most adolescents (69.8%) continued to meet full criteria for ADHD, were known to specialist services and exhibited high levels of antisocial behaviour, criminal activity and substance use problems. Maternal childhood conduct disorder predicted offspring ADHD continuity; maternal childhood conduct disorder, lower child IQ and social class predicted offspring conduct disorder symptoms. CONCLUSIONS: The treatment and monitoring of ADHD need to be intensified as outcomes are poor especially in offspring of mothers with childhood conduct disorder symptoms.