2. Initial Treatment Phase: The dose of the assigned treatment option will be gradually adjusted over the course of the first 3 months until the child's ADHD is well controlled. If the child is assigned to medication, he/she will start with a low dose of the ER MPH product, and it will be gradually increased until his/her ADHD is in good control. Children assigned to medication will be asked to take it every day of the week for at least the first 6 months. Children assigned to behavior therapy will be asked to avoid using medication for the first 6 months of the study. After month 6 if the first treatment is not effective, the child will be given the chance to try the other option. If any treatment is causing a concerning side effect, he/she can stop taking it at any time and we will provide him/her with other treatment options as part of the study.