Executive functioning (EF) is an overarching term that refers to neuropsychological processes that enable physical, cognitive, and emotional self-control. Deficits in EF are often present in neurodevelopmental disorders, but examinations of the specificity of EF deficits and direct comparisons across disorders are rare. The current study investigated EF in 7- to 12-year-old children with autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD) and typical development using a comprehensive battery of measures assessing EF, including response inhibition, working memory, cognitive flexibility, planning, fluency and vigilance. The ADHD group exhibited deficits in vigilance, inhibition and working memory relative to the typical group; however, they did not consistently demonstrate problems on the remaining EF measures. Children with ASD showed significant deficits in vigilance compared with the typical group, and significant differences in response inhibition, cognitive flexibility/switching, and working memory compared with both groups. These results lend support for previous findings that show children with autism demonstrate generalized and profound impairment in EF. In addition, the observed deficits in vigilance and inhibitory control suggest that a significant number of children with ASD present with cognitive profiles consistent with ADHD.