Inclusion Criteria: Patients are included in the study if they participated in a previous qualifying study with modafinil and, in the opinion of the investigator, will continue to benefit from treatment with modafinil. In addition, the following criteria must be met:

• a boy or girl 6 to 17 years of age, inclusive, and English-speaking
• weight and height between the 5th and 95th percentile on the National Center for Health Statistics (NCHS) growth chart for age, height, and weight
• if more than 6 months since last dose of study drug, meets the full DSM-IV crieria for ADHD (combined typd, predominantly inattentive type, or predominantly hyperactive - impulsive type) at screening, as manifested by a psychiatric/clinical evaluation and confirmed by a structured diagnostic interview, namely, the Diagnostic Interview Schedule for Children, Fourth Edition (DISC-IV).
• are in good health (except for a diagnosis of ADHD) as determined by medical and psychiatric history, physical examination, ECG, serum chemistry, hematology, urinalysis
• girls of child bearing potential (Tanner scale >3) OR all girls 8 years of age and older have a negative urine pregnancy test at screening, must be using a medically acceptable method of birth control, and must agree to continue use of this method for the duration of the study (and for 30 days after participation in the study). (NOTE: For conducting pregnancy tests, the investigator has the option of determining the sexual maturity all girls 8 years of age and older.) Acceptable methods of birth control include: barrier method with spermicide; steroidal contraceptive (eg, oral, transdermal, implanted, and injected) in conjunction with a barrier method; intrauterine device (IUD); or abstinence
• have a parent or legal guardian who is willing to participate in the study.

Exclusion Criteria: Patients are excluded from participating in this study if 1 or more of the following criteria are met:

• a history or current diagnosis of pervasive developmental disorder, schizophrenia, or other psychotic disorders, or a clinical assessment of current suicide risk
• any current psychiatric comorbidity, including but not limited to depression or other mood disorder, anxiety disorder, or pervasive mental disorder, that requires pharmacotherapy
• a clinically significant drug sensitivity to stimulants such as amphetamine, dextroamphetamine, methylphenidate, pemoline
• failure to respond to 2 or more adequate courses (dose or duration) of ADHD therapy
• use of any other prescription medications for ADHD (e.g., amphetamine, dextroamphetamine, methylphenidate, pemoline, atomoxetine) after the screening visit
• use of any MAO inhibitors or SSRIs within 2 weeks of the baseline visit
• hypertension, defined as follows (SBP = systolic blood pressure and DBP = diastolic blood pressure):
• ages 6-9 years SBP > 122mmHg or DBP>78mmHg
• ages 10-12 years SBP > 126mmHg or DBP>82mmHg
• ages 13-17 years SBP > 136mmHg or DBP>86mmHg
• hypotension, defined as sitting systolic blood pressure (taken after resting for 5 minutes) of less than 50mmHg for children under 12 years of age or less than 80mmHg for children 12 and older
• a sitting pulse outside the range of 60 through 115 bpm after resting for 5 minutes