Individuals with Attention Deficit Hyperactivity Disorder (ADHD) have difficulties with sustaining attention, being overactive and being impulsive. It is one of the most common childhood disorders and causes difficulties in school, and with family relationships and friendships, whilst those with ADHD are also at higher risk of other difficulties such as anxiety and depression both in childhood and later life. Not all individuals with ADHD have the same problems though, so it is important to understand who is at greatest risk of them. Difficulties with attention or hyperactivity are present across many people whilst only some have sufficient problems to be diagnosed with ADHD. International guidelines indicate where the dividing line between having a diagnosis or not is set, but we know that individuals who do not meet this diagnostic threshold can still have difficulties due to their ADHD symptoms whilst even in those with a diagnosis, the specific constellation of problem behaviours differs between individuals. This project aims to examine how differences in the symptom presentation and impairments in children are linked to other difficulties they have in childhood and as they grow into adulthood. It will also look at how genetic risks for ADHD and other disorders are related to these different presentations. This will be examined in both the general population (the ALSPAC cohort) and a clinical sample of children with ADHD, with additional replication in other international cohorts.