Study to Evaluate the Efficacy of Modafinil Treatment in Patients With Attention Deficit Hyperactivity Disorder (ADHD) Who Are Responders to Modafinil Treatment

Inclusion Criteria: * Patients must be currently enrolled in a Cephalon-sponsored clinical study and have completed at least 12 months of continuous modafinil treatment. Patients will be included in the study if they continue to meet all applicable criteria in their previous study and all of the following criteria are met: * Written informed consent/assent is obtained. * The patient is currently enrolled in study C1538d/312/AD/US or C1538/3044/AD/US and received modafinil treatment, continuously, for at least 12 months. * The patient meets the protocol criteria for response at each of the last 2 visits of their previous study. Patients from study C1538d/312/AD/US must have at least a 25% reduction in Attention-Deficit/Hyperactivity Disorder Rating Scale - IV \[ADHD-RS-IV\] (Home Version) total score compared with the original baseline (this must be the baseline for a previous double-blind, placebo-controlled study of modafinil in ADHD). Patients from study C1538/3044/AD/US must have at least a 25% reduction in total score of the ADHD Index subscale of the Conners' Parent Rating Scale: Revised, Short Form (CPRS:R-S), compared with the baseline value from study C1538/3044/AD/US. * The patient is in good health (except for diagnosis of ADHD) as determined by medical and psychiatric history, physical examination, electrocardiograms (ECGs), serum chemistry, hematology, urinalysis, and vital signs. * Girls who are post-menarche or sexually active must have a negative urine pregnancy test at the baseline visit, 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). Acceptable methods of birth control include the following: barrier method with spermicide; steroidal contraceptive (eg, oral, transdermal, implanted, or injected) in conjunction with a barrier method; intrauterine device (IUD); and abstinence. * The patient has 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: * The patient has a history or current diagnosis of pervasive developmental disorder, schizophrenia, or other psychotic disorders, or positive clinical assessment of current suicide risk or ideation. * The patient has any current psychiatric co-morbidity that requires pharmacotherapy, including but not limited to depression or other mood disorder, anxiety disorder, or pervasive mental disorder. * The patient currently uses any other prescription medication, other than modafinil, for ADHD (eg, amphetamine, dextroamphetamine, methylphenidate, pemoline, atomoxetine). * Previous exposure to modafinil caused any clinically significant (drug-related) adverse reaction that led to withdrawal from the study, or which the investigator considers likely to put the patient at risk.