There are three major types of attention deficit hyperactivity disorder (ADHD) usually diagnosed in children. They include:

• Predominantly inattentive ADHD (ADHD/I). Marked by difficulty paying attention. Patients may struggle to concentrate and complete tasks and may be forgetful and easily distracted. They tend to have poor organizational skills and may appear to be lethargic, sluggish, shy, anxious or constantly daydreaming. This condition is most often diagnosed in adolescent girls, and is diagnosed if six or more symptoms of inattention have persisted for more than six months, according to the American Psychiatric Association (APA).
  
  
• Predominantly hyperactive/impulsive ADHD (ADHD/HI). Marked by difficulty controlling behavior, with an increased risk for serious aggressive or oppositional behavior and antisocial conduct. Patients often fidget and are excessively restless. They may blurt out comments that are inappropriate and often do not think before they act. This condition is diagnosed if six or more symptoms of hyperactivity and impulsivity have persisted for more than six months.
  
  
• Combined ADHD. Combines symptoms of the other two forms of ADHD. It is the most common form of ADHD. This condition is most often diagnosed in boys of elementary-school age. It is diagnosed when six or more symptoms associated with each of the two major forms of ADHD are present.