The male to female ratio of ADHD is 4:1. This chapter on ADHD provides a wide perspective on understanding, diagnosis and treatment for ADHD. It relies on a neurodevelopmental perspective of ADHD. Signs and symptoms of ADHD are described through the DSM-V criteria. A case example (K, a patient of mine) is illustrated throughout the chapter to provide context and illustrations, and demonstrates the relative merits of "doing" (i.e. behavioural interventions) compared to cognitive insight, or medication alone. Finally, a discussion of the Cognitive Behavioral Modification Model (CBM) for the treatment of ADHD provides a snapshot of interventions used by clinicians providing psychological help.