Abstract: Researchers have postulated that executive dysfunction is the primary cognitive deficit that best explains autism's core symptoms. More recently, research has reported that a strong association exists between executive function skills and other autism deficits. The frontal lobes, which play an essential role in executing complex actions, are thought to mediate executive functions as well as the ability to use knowledge and skills adaptively. The aim of the current study was to examine the relationship between executive function deficits and adaptive behavior in children with Autistic Disorder (AD) as well as to determine whether the relationship is mediated by cognitive function. Sixteen children with AD were compared to 17 normal control children. The study replicated well-established executive function deficits of cognitive flexibility and planning in children with AD even after removing the influence of fluid intelligence. In addition, the results showed that a measure of global executive function and verbal cognitive ability significantly predicted adaptive behavior in children with autism. Results also indicated that a variable measuring cognitive flexibility was not significantly related to adaptive skills, while a task that measures planning ability was significantly related to community living adaptive skills. Although the relationship between planning and adaptive behavior was not statistically significant once fluid intelligence was controlled, the planning variable continued to account for a large portion of variance in the adaptive skills. Due to finding heterogeneity in several variables, as evidenced by large standard deviations, the autistic group was further examined for individual differences. The results of the current study indicated that cognitive ability and executive functions can predict and contribute to adaptive skills; however, various cognitive contributions and the metric used to measure abilities limits their relationship to adaptive skills. It is important to be conscious of the metric used to measure abilities and to assess multiple cognitive components, including executive functions and IQ, in relation to their contributions to the behavioral manifestations of autism. Furthermore, the divergent profile of deficits in different cohorts of individuals with autism may point to a polygenetic disorder or a varying phenotype within autism.