Objective: To investigate characteristics of attention in children with the combination of autism spectrum disorder (ASD) and ADHD. Method: Four groups of 8- to 10-year-old children were compared on the Conners’ Continuous Performance Test-Second Edition (CCPT-II): (a) ASD + ADHD (n = 11), (b) ASD only (n = 9), (c) ADHD only (n = 38), and (d) no diagnosis (n = 134). Results: There was an overall effect of group on the Continuous Performance Test (CPT) index and measures of hit reaction time, accuracy, response style, variability, and consistency. The ASD + ADHD group, much like the ADHD only group, had a more risky response style, a higher variability, and a lower consistency than the ASD only group. The impact of intellectual function on CCPT-II performance was considerable in children within the ASD subgroups. Conclusion: The findings underscore the importance of including measures of attention and intellectual function when assessing children with the combination of ASD and ADHD.