Adult Attention Deficit Hyperactivity Disorder (A-ADHD) is one of the psychiatric disorders which awareness is growing. The exact causes of A-ADHD are still unknown. In addition to neurochemical and neuroanatomic disorders, genetic and environmental factors are discussed in its etiology. In our study, we aimed to evaluate the oxidative status of A-ADHD patients and investigate whether oxidative metabolites can be used as diagnostic tools or not in A-ADHD. Blood samples were taken from enrolled 50 A-ADHD patients and 31 controls in appropriate way and Total Antioxidative Status (TAS), Total Oxidative Status (TOS), and Oxidative Stress Index (OSI) were studied in Harran University Biochemistry Labs. Results were compared between groups and ROC curve was drawn in order to evaluate diagnostic performances. Patients' TAS, TOS and OSI were significantly higher than controls. There was not a significant difference between comorbid cases and only A-ADHD patients in terms of measured values. A-ADHD can be predicted for TOS over 9.8575 mu mol H2O2 Eqv./L level with 86% positive predictive value and %100 negative predictive value. In A-ADHD, oxidative balance is impaired. High antioxidant levels may be compensatory against the oxidant increase. Oxidative parameters may be used in A-ADHD diagnosis. (C) 2011 Elsevier Ltd. All rights reserved.