Inclusion Criteria:

1. Male and female outpatients older than 18 and younger than 55 years of age.
2. Subjects with the diagnosis of attention deficit hyperactivity disorder (ADHD), by DSM-IV, as manifested in clinical evaluation and confirmed by structured interview.
3. ADHD Symptom Checklist score > 24.
4. Patients with past history of depression, bipolar disorder, anxiety disorder (including OCD) without current disorder for > 3 months as ascertained through structured diagnostic interview and clinical exam.
5. Subjects treated for anxiety disorders and depression who are on a stable medication regimen for at least three months, and who have a disorder-specific CGI-Severity score ≤ 3 (mildly ill) and who have a score on the Hamilton-Depression and Hamilton-Anxiety rating scales below 15 (mild range).
6. Subjects with a past history of tics but tic free for > 1 year.
7. Subjects with past history of substance use disorders but substance free for > 6 months.
8. Subjects receiving non-MAOI antidepressants (e.g., SSRI's, bupropion, venlafaxine) or benzodiazepines who have been on a stable regimen for > 3 months for any of the conditions listed above.

Exclusion Criteria:

1. Any clinically unstable psychiatric conditions including the following: acute psychosis, acute panic, acute OCD, acute mania, acute suicidality, bipolar disorder, acute substance use disorders (alcohol or drugs, sociopathy, criminality, or delinquency.
2. Any metabolic, neurological, hepatic, renal, cardiovascular, hematological, opthalmic, or endocrine disease.

3. Clinically significant abnormal baseline laboratory values which include the following:

   1. Values > 20% above the upper range of the laboratory standard of a basic metabolic screen.
   2. Exclusionary blood pressure > 140 (systolic) and 90 (diastolic).
   3. Exclusionary ECG parameters: QTC > 460 msec, QRS > 120 msec, and PR > 200 msec. Subjects having ECG evidence of ischemia or arrhythmia as reviewed by an independent cardiologist.
4. Mental retardation (IQ <75).
5. Organic brain disorders.
6. Seizures or tics in the last year.
7. Pregnant or nursing females.
8. Subjects with current adequate treatment for ADHD or a history of a previous adequate trial of Concerta.

9. Non-English speaking subjects will not be allowed into the study for the following reasons:

   1. the assessment instruments are unavailable and have not been adequately standardized in other languages;
   2. our clinical trials facility is located in Cambridge and not at the MGH main campus; thus translators are unavailable;
   3. even if such translation services were available, the assessments in the English language conducted by English-speaking clinicians and raters with English-speaking subjects are already extremely time-consuming, lasting many hours, making it unfeasible, unrealistic, and of dubious clinical validity to conduct them with a translator with non-English-speaking subjects;
   4. psychiatric questionnaires and evaluations are taxing, and adding the complexity of a translator has the potential to make the patient experience even more exhausting