This research investigates the Attention Deficit/Hyperactivity Disorder (ADHD) in a school context from a dimensional perspective. It took part of the study 107 children with mean age of 12,37 years. It was used the ADHD's Scale - teacher's version and an adapted form for parents in addition to computer tasks to measure cognitive processing. The prevalence of Hyperactivity, according to teachers and parent's report, was consistent with the literature (4,7%). Attention deficit correlated with all measures of cognitive processing. Hyperactivity and Antisocial Behavior correlated with working memory measures only when the first was assessed by teachers and the second was assessed by parents. In this sense, it was found low concordance between informants regarding ADHD behavior dimensions. However, teacher's report seems to be according with contemporary literature. It was concluded that dimensional investigation can provides relevant information related to demographic and cognitive characteristic of ADHD.