This guideline covers recognising, diagnosing and managing attention deficit hyperactivity disorder (ADHD) in children, young people and adults. It aims to improve recognition and diagnosis, as well as the quality of care and support for people with ADHD. In September 2019 we amended the recommendation on assessment for people starting medication for ADHD to indicate that an ECG is not needed before starting stimulants, atomoxetine or guanfacine if cardiovascular history and examination are normal and the person is not on medicine that poses an increased cardiovascular risk. For details, see update information.