ADHD is a descriptive term covering a heterogeneous condition characterised by hyperactivity, impulsivity and inattention that is enduring, pervasive (occurring across different situations) and impairs function. It begins early in life, under seven years of age. It is often associated with comorbidity, including disturbed behaviour, anxiety, autism spectrum disorders, learning disability and other problems. The diagnosis should be made by an experienced, trained specialist, based on information gathered from a number of sources; it cannot be made on the basis of behavioural scales alone. Referral pathways can facilitate diagnosis and management by clarifying professional roles and responsibilities.