Learning disability (mental retardation) can be defined as IQ <70 combined with impairment in social functioning. ADHD is more common in people with learning disability and the prevalence increases as the degree of learning disability increases. However, assessment of ADHD in people with learning disability can be problematic and needs to be undertaken carefully. ADHD occurs more commonly in specific syndromes associated with learning disability. It is also common in people with epilepsy, a condition which occurs more frequently in people with learning disability. Correct management of ADHD in an individual with learning disability depends on careful assessment followed by an approach that is both comprehensive and pragmatic; for example, people with learning disability may be unable or unwilling to swallow tablets, implying that a different formulation or different strategy of medication administration may be required. Despite the challenges, treating ADHD in people with learning disability can be both effective and worthwhile.