Atomoxetine (Strattera®) is recommended for use within NHS Wales for the initiation of treatment in adults with attention deficit hyperactivity disorder (ADHD). Treatment must be initiated by a specialist in the treatment of ADHD, such as a paediatrician, child/adolescent psychiatrist, or psychiatrist. Diagnosis should be made according to current Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria or the guidelines in International Classification of Mental and Behavioural Disorders (ICD). In adults, the presence of symptoms of ADHD that were pre-existing in childhood should be confirmed. Third-party corroboration is desirable and atomoxetine should not be initiated when the verification of childhood ADHD symptoms is uncertain. Diagnosis cannot be made solely on the presence of one or more symptoms of ADHD. Based on clinical judgment, patients should have ADHD of at least moderate severity as indicated by at least moderate functional impairment in two or more settings (for example, social, academic, and/or occupational functioning), affecting several aspects of an individual’s life.