Introduction: Attention Deficit Hyperactivity Disorder (ADHD) constitutes a high prevalence disorder.  The effect of intelligence in vigilance tasks has been studied, with discordant results.  Therefore we are interested in comparing the Conners´ Continuous Performance Test II (CPTII) performance according to intellectual performance.

Objective:To analyze CPT II profiles in children with ADHD in relation to their intellectual performance (IP).

Methods and Materials: Descriptive, analytical, cross sectional study.  We included patients with ADHD diagnosis (DSM IV). Patients were divided into two groups according to their Full scale intellectual quotient (FIQ, Weschler scale): Normal intellectual performance (IP) for those with FIQ 80 and above, or low IP for those with FIQ 79 or below. The Conners´ Parent Rating Scale - Revised (short version) was also administered.

Results: 125 patients were included, 72% belonged to the normal IP group. The age in this group was lower (9.4 years vs 10.5; p=0.03), and the FIQ score was 93.25 vs. 68.42 (p<0.001). Patients from the low IP group presented more omissions when compared to normal IP group (63.28 vs 54.87;p< 0.02) and slower response time (66.28 vs. 55.86;p<0.001).  Both groups reported above cut-off scores for inattention and hyperactivity indexes in Conners´scale.

Conclusion: Profiles in CPT differed according to Intellectual Performance.  We observed that CPTII was more useful in detecting attention failures in patients with low IP, despite the fact that both groups had clinical indicators of inattention.