The primary objective of this study is to investigate the relative efficacy and tolerability of omega-3 fatty acid supplementation, more specifically docosahexaenoic acid (DHA), in reducing attention-deficit/hyperactivity disorder (ADHD) symptoms in children. The present study is going to determine whether DHA supplementation induces modifications in fatty acid blood level and to evaluate the correlation between this possible modification and behavioral, neuropsychological and functional indexes. The study is a randomised, placebo-controlled double-blind intervention trial providing within- and between-group comparisons over 6 months. At the start of the study, the patients will be randomized to active treatment with DHA in a dose of one capsules twice daily, corresponding to a daily dose of 500 mg DHA, or to placebo (identical capsules with fishy odor containing 500 mg wheat germ oil). A total of 50 patients will be included in the study which is conducted in the Child Psychiatry Unit of "E. Medea" Scientific Institute (in northern Italy). The study participants are recruited from among patients assessed and diagnosed at this clinic, aged 6 to 14 years, who met DSM-IV criteria for a diagnosis of ADHD of any subtype (see Eligibility Criteria for further details). The study will also recruit 20 typically developing children to provide a control group at the start of the research for comparison of fatty acid blood level and other outcome measures (healthy children will not be included in the supplementation phase).

Clinical assessment will be made were made at three visits at the site: at baseline (Visit 1), 4 months (Visit 2) and 6 months (Visit 3). At Visits 1-2-3, a blood sample will be taken for analysis of the blood fatty acid profile. At Visit 1, informed consent is signed, inclusion and exclusion criteria are assessed, and the investigators make a medical evaluation, including medical and psychiatric history, assessment of diagnosis and comorbidity through parent interview according to DSM-IV criteria (DAWBA). A number of other examinations and instruments will be used, including height and weight, pulse and blood pressure, a neuromotor examination and an assessment of the general level of functioning with clinical scales and questionnaires completed by parents (see Outcome Measure Section for more details); several neuropsychological tests and reading test will be performed by a developmental neuropsychologist. At Visits 1-2, changes in the concentration of oxygenated Hb and deoxygenated Hb in prefrontal cortex during a computerized visual working memory task will be assessed in a subset of patients (10 children from each group) with functional Near-Infrared Spectroscopy. Visit 2 will included the same examinations and instruments as Visit 1, with the exception of the reading test; Visit 3 will included all the same measures as Visit 1, with the exception of the fNIRS. Parents will return every month at the clinic to assess the compliance (defined as taking the prescribed dosage on more than 70% of the days in the interval), to be interviewed about current medical symptoms and any adverse events or side effects, and to get the supplementation dosage for the following month.