Purpose: To evaluate the intellectual performance of children diagnosed with ADHD and analyze the efficiency of WISC-III. Methods: 30 children diagnosed with ADHD (23 with ADHD only and 7 with ADHD and comorbidity, both gender, and ages between 7 and 16 years old, proceeding from the SEPIA-IPq-HCFMUSP. Results: The groups showed difficulties in the following subtests: Information, Coding and Arithmetic when they were compared with normative sample. However, when both groups were compared with normative sample we verified that only the group with ADHD only presented difficulties in two subtests: Digit span and Symbol Search. Discussion: Although this study has not found significant differences in the general indexes, it's possible to state that below average performance in Information, Arithmetic, Coding, Digit span and Symbol Search can suggest weakness, in this group, related to attentional amplitude, concentration and processing speed which result in difficulties in acquiring new information