The central problems here involve Inattention, i.e. persistent difficulties with sustained attention and concentration, and/or Hyperactivity-Impulsivity. Hyperactive-Impulsive children show excessive motor activity and restlessness, an inability to regulate behaviour according to the situation, and difficulty delaying gratification.

Attention problems are not always so obvious unless they occur together with hyperactivity, but these alone can create equally serious problems of under-achievement. A large proportion of ADHD children (around 50%) also show clinical features of dyslexia and/or dyspraxia, as noted above, although these associations are stronger for the Inattentive form of ADHD than for Hyperactivity-Impulsivity.