Background:Attention deficit hyperactivity disorder(ADHD)is a neurodevelopmental disorder manifesting in early life.These children are more vulnerable to sexual abuse as victims and offenders.Here we describe a teenager with previously undiagnosed ADHD presenting with an alleged act of sexual offending.Case report:According to the 14-year-old accused,he has engaged in penetrative anal intercourse with another school colleague.He also divulged past such incidents involving a teenage male relative and insertion of foreign bodies by him to his anus repeatedly.On assessment the accused had features of inattention such as difficulty in sustaining attention,failing to finish work and features of impulsivity such as difficulty waiting for his turn and intruding on others.He was diagnosed with ADHD according to DSM 5 clinical criteria which were supported by the Sinhalese adaptation of the Swanson,Nolan and Pelham questionnaire.The assessment of the non-verbal intelligence was in the normal range,but his school performance was far below the average.Discussion:Undiagnosed ADHD contributes to academic impairment and inappropriate sexual behaviour.It is possible that the described adolescent’s impulsiveness and inattention contributed to his academic failure and risky sexual behaviour.Early detection and proper management of this disorder may have reduced the risk of such behaviour in him.