In this study, we compared neuropsychological tests and parent-based ratings of flexibility in a sample of children with autism spectrum disorders (ASD). We investigated the discriminant validity of the domain-specific flexibility measures by comparison with the domain general measures, general behavioral problems, general ASD-related traits, and general intelligence. Tests and parent-based ratings of flexibility were not significantly correlated. Parent-based ratings were strongly related with the three broadband measures, whereas the discriminant validity indices of the neuropsychological tests were satisfactory. These findings suggest that parent-based ratings do not reflect the specific executive construct of flexibility, but instead reflect a broad spectrum of general child characteristics.