There are 5 types
According to the dsm-iv-tr there are 5 types of adhd
: predominantly hyperactive/impulsive subtype, predominantly inattentive subtype, combined subtype, persistent into adulthood, and not other wise specified.
The most common is the inattentive subtype by a wide margin, and is the subtype frequently missed. See http://www.Behavenet.Com/capsules/disorders/adhd.Htm.