Attention Deficit Hyperactivity Disorder (ADHD) is generally considered to be a developmental disorder, largely neurological in nature, affecting 3–5 percent of the population. The disorder is characterized by a persistent pattern of inattention and/or hyperactivity-impulsivity. ADHD initially appears in childhood and manifests itself with symptoms such as hyperactivity, forgetfulness, poor impulse control, and distractibility. ADHD is currently considered to be a persistent and chronic syndrome for which no medical cure is available. ADHD is most commonly diagnosed in children and, over the past decade, has been increasingly diagnosed in adults. It is believed that around 60% of children diagnosed with ADHD retain the disorder as adults. Studies show that there is a familial transmission of the disorder which does not occur through adoptive relationships. Twin studies indicate that the disorder is highly heritable and that genetics contribute for about three quarters of the total ADHD population. While the majority of ADHD is believed to be genetic in nature, roughly about 1/5 of all ADHD cases are thought to be acquired after conception due to brain injury caused by either toxins or physical trauma prenatally or postnatally.

According to a majority of medical research in the United States, as well as other countries, ADHD is today generally regarded to be a non-curable disorder for which, however, some effective treatments are available. Over 200 controlled studies have shown that stimulant medication is an effective way to treat the symptoms of ADHD. Methods of treatment usually involve some combination of medication, behaviour modification, life style changes, or counselling. Certain social critics are skeptical that the diagnosis denotes a genuine impairment or disability. The symptoms of ADHD are not as profoundly different from normal behavior as is often seen with other mental disorders. Still, ADHD has been shown to be impairing in life functioning in several settings and many negative life outcomes are associated with ADHD.
ADHD is a developmental disorder that largely is neurological in nature. The term developmental means that certain traits such as impulse control significantly lag in development when compared to the general population. This developmental lag has been estimated to range between 30-40 percent in comparison to their peers; consequently these delayed attributes are considered an impairment. ADHD has also been classified as a behavioral disorder and a neurological disorder or combinations of these classifications such as neurobehavioural or neurodevelopmental disorders. These compounded terms are now more frequently used in the field to describe the disorder. The behavioral classification for ADHD is not completely accurate in that those with Predominately Inattentive ADHD often display little or no overt behaviors.

ADHD can be treated by psychiatrists and neurologists; some practitioners of this type specialize in treating children with ADHD and others specialize in the treatment of adults with ADHD. Children's hospitals that have psychiatric units with programs dedicated to treating ADHD are often a good place to receive treatment, but a psychiatrist's or neurologist's office will generally have staff who can understand and treat ADHD effectively.

A pediatric psychiatrist or neurologist can provide the child’s school with a written ADHD diagnosis that informs the school of accommodations that may aid the student in academic endeavors. In the United States, an educational institution must make accommodations for a child with ADHD when the educational institution is provided with diagnostic documentation signed by a physician (see section 503 of American Disabilities Act).

Accommodations may include:

Extended time for taking exams
Extended due dates for homework
A distraction-free environment during examination
Permission to record lectures
Copies of lecture notes
ADD Coaching is a specialized type of life coaching that uses specific techniques geared toward working with the unique brain wiring of individuals with Attention-deficit hyperactivity disorder.

Coaches work with clients to help them better manage time, organize, as well as start (and finish) projects. There is also an element of education, as each client learns better how their AD/HD affects them. Coaches put emphasis on finding individual strengths, and using those strengths more often, while finding "work-arounds" for dealing with of challenge. Coaches also help clients get a better grasp of what reasonable expectations are for them as individuals, since people with ADD or AD/HD "brain wiring" often seem to need external mirrors for accurate self-awareness about their potential despite their apparent "limitations."

While some ADD Coaches work with clients in person, many do phone coaching only, which (in theory) allows clients to find the best coach for themselves, regardless of location. A good fit between client and coach (as well as between coach and coach training) is essential, and there are advantages to working over the phone, for both client and coach.
To meet the diagnostic criteria according to the DSM-IV (Diagnostic and statistical Manual of psychiatric disorders) a couple of aspects have to be considered to meet a diagnosis of adhd:
A. Six (or more) of either 1) Inattention, or 2) Hyperactivity/Impulsivity Symptoms must have persisted for at least 6 months to a degree that is maladaptive and inconsistent with developmental level:

1) Inattention

often fails to give close attention to details or makes careless mistakes in homework, work, or other activities
often has difficulties sustaining attention in tasks or play activities
often does not seem to listen when spoken to directly
often does not follow through instructions and fails to finish schoolwork, chores, or duties in the workplace (not due to oppositional behavior or failure to understand instructions)
often has difficulties organizing tasks and activities
often avoids, dislikes or is reluctant to engage in tasks that require sustained mental efforts
often loses things necessary for tasks or activities (e.g. toys, school assignments, pencils, books)
is often easily distracted by extraneous stimuli
is often forgetful in daily activities
2) Hyperactivity/Impulsivity

Hyperactivity

often fidgets with hands or feet or squirms in seat
often leaves seat in classroom or in other situations in which remaining seated is expected
often runs about or climbs excessively in situations in which it is inappropriate (in adolescents or adults, may be limited to subjective feelings of restlessness)
often has difficulty playing or engaging in leisure activities quietly
is often "on the go" or often acts as if "driven by a motor"
often talks excessively
Impulsivity

often blurts out answers before questions have been completed
often has difficulty awaiting turn
often interrupt or intrudes on others (e.g. butts into conversations or games)
B) Some symptoms causing impairment were present before age 7 More.

C) Some impairment from the symptoms is present in two or more settings (e.g. at school and at home) More.

D) There must be clear evidence of clinically significant impairment in social, academic or occupational functioning More.

E) Occurrence is not exclusively during the course of a Pervasive Developmental Disorder, Schizophrenia or other Psychotic Disorder

The asessment of whether a person has ADHD or not must be done by a psychiatrist who is an expert on ADHD.