ADHD is a neurobehavioral developmental disorder. An individual with ADHD finds it much more difficult to focus on something without being distracted. He has greater difficulty in controlling what he is doing or saying and is less able to control how much physical activity is appropriate for a particular situation compared to somebody without ADHD. In other words, a person with ADHD is much more impulsive and restless. Health care professionals may use any of the following terms when describing a child (or an older person) who is overactive and has difficulty concentrating - attention deficit, attention deficit hyperactivity disorder, hyperkinetic disorder, hyperactivity.