According to the American Psychiatric Association, ADD, also commonly known as ADHD, attention deficit hyperactivity disorder, is comprised of two distinct conditions: inattentiveness and/or hyperactivity/impulsivity.

A person is diagnosed with inattentive ADD if he or she exhibits six or more symptoms of inattention for at least six months, if that inattentiveness interferes with normal function, and if it is inappropriate to the age level. The behaviors are considered symptoms of ADD only if they are exhibited on a regular basis — for instance, if the child "often fails to give close attention to details or makes careless mistakes in schoolwork, work, or other activities."

Other symptoms could include difficulty paying attention to tasks; not listening when spoken to directly; not following through on instructions; failing to finish tasks; having difficulty organizing tasks; often avoiding tasks, such as homework, that require sustained concentration; often losing things needed for activities or tasks; being easily distracted; and often being "forgetful in daily activities."

Hyperactivity/impulsivity is diagnosed when a person exhibits six or more of the following symptoms for at least six months on a regular basis, and once again the behavior interferes with normal function and is inappropriate to the age level.

Symptoms include fidgeting and inability to sit still; getting up in the middle of class or other activity; running around inappropriately; having difficulty playing quietly; talking excessively; blurting out answers; having difficulty awaiting a turn; and interrupting or intruding on others.

In either case, the severity of symptoms must be inconsistent with developmental level and must cause clinically significant impairment in two or more settings (i.e., at school or work, and at home).

Some of the symptoms must have been present before the age of 7, and the conditions must be independent of other serious psychological disorders (e.g., schizophrenia or other psychotic disorders). A combined diagnosis is also possible, that is, both inattentiveness and hyperactivity/impulsivity in one individual.