Impaired WM is a central deficit in ADHD. A computerized training program, Cogmed, has been shown to increase WM capacity in children with ADHD. It is not known whether the training improves behavior associated with classroom learning, such as remaining on-task and inhibiting off- task behavior. The aim of this study is to utilize ecologically valid measures to investigate training's effect on observable ADHD behavior in conjunction with more standard measures. Subjects will be randomly assigned to a Cogmed versus an active "placebo" condition in which the tasks do not increase in difficulty level in a double-blinded fashion. The effects of the active Cogmed versus placebo computer training will be compared on measures in children with ADHD.

Inclusion Criteria:

1. Age range 7-14
2. At least average academic and intellectual functioning via parent report.
3. Must have ADHD (by parent report of previous diagnosis or per telephone screening checklist - to be confirmed via interview and ratings)
4. Attentional, hyperactive or impulsive symptoms that interfere with functioning.

Exclusion Criteria:

1. Diagnosis of severe mental illness for example, psychotic, bipolar or major depressive disorder, (by history)
2. Mental retardation (by history)
3. English is not the primary language
4. Family does not have a computer