The American Academy of Pediatrics is the leading organisation in determining policy in everything related to diagnosing and treating pediatric diseases. The organisation has published a series of guidelines in regards to the diagnoses and treatment of children suffering from ADHD. The latest paper published by the AAP can be found in the follwing link

http://pediatrics.aappublications.org/content/early/2011/10/14/peds.2011-2654