To determine if a sample of children meeting diagnostic criteria for a Pervasive Developmental Disorder (PDD) display symptoms and impairment related to Attention Deficit Hyperactivity Disorder (ADHD) sufficient to warrant a comorbid diagnosis of ADHD. Further, do children with PDD displaying such symptoms demonstrate more impairment in daily life activities than those children only having PDD? Method: A retrospective chart review was conducted on children (N = 57) diagnosed with the PDD's of Autism or PDD-Not Otherwise Specified (PDD-NOS), or ADHD. Comparative analysis of questionnaire and neuropsychological test data was completed to determine the severity of ADHD-like symptoms presenting among children with PDD. Results: From the pool of subjects having PDD with sufficient data (N = 27), 7 or 26% met DSM-IV criteria for the combined type of ADHD. Nine or 33% met diagnostic criteria for the Inattentive Type of ADHD and 11 or 41% did not demonstrate a significant number of ADHD symptoms to warrant a comorbid diagnosis of ADHD. Results indicate that a subgroup of children with PDD displaying significant ADHD-like symptoms may in fact have ADHD thus warranting a comorbid diagnosis of ADHD. Current data did not suggest children with PDD and the combined type of ADHD demonstrated significantly more impairment in daily life functioning than those children only having PDD. However, this appeared likely the result of small sample size. The data, however, does indicate such children experience more difficulties in daily situations as rated by parents and teachers. Conclusion: These findings reinforce clinical observations indicating that some children with PDD may also experience an independent comorbid condition of ADHD, suggesting that a comorbid diagnosis of ADHD with PDD be considered in such cases. If further findings are replicated, the current exclusionary DSM-IV-TR criteria of making such a comorbid diagnosis should be re-considered.