This study will consist of a six-week open-label treatment period with an extended duration methylphenidate (OROS MPH) followed by subsequent monthly visits for 24 months in a large sample of youths aged 12-17 who meet Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for ADHD.

The researchers hypothesize that OROS MPH treatment will be associated with low rates of cigarette smoking in ADHD youth.

Inclusion Criteria:

1. Adolescent outpatients between 12 to 17 years of age (inclusive).
2. Subjects with the DSM-IV diagnosis of ADHD, as manifested in the clinical evaluation and confirmed by structured interview.
3. Subjects with sufficient current ADHD symptoms to warrant treatment, as measured by a Clinical Global Impression Severity Scale (CGI-S) score of greater than or equal to 4 (moderately ill); OR subjects already on Concerta who are judged to be responders (CGI of 1 or 2) and who tolerate treatment well.

Exclusion Criteria:

1. Any serious or unstable medical illness including hepatic, renal, gastroenterologic, respiratory, cardiovascular (including ischemic heart disease, hypertension), endocrinologic, neurologic, immunologic, or hematologic disease.
2. Clinically significant abnormal baseline laboratory values
3. History of seizures
4. Active tic disorder
5. Pregnant or nursing females
6. Mental retardation (intelligence quotient [IQ] < 75)
7. Organic brain disorder
8. Eating disorders
9. Psychosis
10. Current bipolar disorder (current episode)
11. Current depression > mild (CGI-S > 3)
12. Current anxiety > mild (CGI-S > 3)
13. Substance abuse or dependence within the past 2 months
14. Recent change in non-monoamine oxidase inhibitor (MAOI) antidepressants (< 3 months)
15. Recent change in benzodiazepines (< 3 months)
16. Concerta non-responder

The main limitation of this report stems from its uncontrolled, open-label design. Thus, we cannot assert a causal relationship between lower smoking rates and OROS MPH prescription.