There are three subtypes of ADHD defined in the DSM-IV based on types of symptoms displayed: combined, primarily inattentive and primarily hyperactive/impulsive.7 In the combined subtype, the patient displays symptoms consistent with both inattention and hyperactivity/impulsivity and typically has the most symptoms. This is the most common subtype and about which the most is known. The primarily inattentive subtype is the second most common and was formerly known as Attention Deficit Disorder (ADD). This subtype demonstrates a more equal distribution between males and females. Some children will be initially diagnosed with this subtype and when symptoms associated with hyperactivity/impulsivity become apparent, the diagnosis may change to the combined subtype. Conversely, when children initially diagnosed with the combined subtype 'outgrow' the hyperactivity, the diagnosis may change to this subtype. The primarily hyperactive subtype frequently describes very young children who may have the combined subtype but have not reached the age where inattention becomes evident.