Inattention and hyperactivity/impulsivity are the key behaviors of ADHD. Some people with ADHD only have problems with one of the behaviors, while others have both inattention and hyperactivity-impulsivity. Most children have the combined type of ADHD. Individuals with problems with inattention may wander off task, lack persistence, have difficulty sustaining focus, and are disorganized; and these problems are not due to defiance or lack of comprehension.
Individuals with hyperactivity seem to move about constantly, including in situations in which it is not appropriate; or excessively fidget, tap, or talk. In adults, it may be extreme restlessness or wearing others out with constant activity. A person who is impulsive makes hasty decisions without first thinking about them and these decisions often lead to harmful consequences. It is normal to have some inattention, unfocused motor activity and impulsivity, but for people with ADHD, these behaviors are more severe, occur more often, and interfere with or reduce the quality of how they function socially, at school, or in a job.