Objective: New diagnostic criteria of Autism and the prevalence of Autism are raising a lot of questions. Parents, educators and medical professionals are searching for answers to determine which child should be diagnosed with Autism Spectrum Disorder (ASD) and qualify for related services. Neuropsychologists are in a unique position to help differentiate ASD from other developmental disorders using objective neuropsychological (NP) tools to elicit and accurately measure deficits and strengths. Method: Case A: A 4 year-old boy with developed language and academic skills and absence of repetitive movements experiences behavioral difficulties in school. Pediatrician diagnosed ADHD. NP testing revealed mild deficits in social communication and interaction and rigid thinking, which contribute to his behavioral problems. Case B: A 4 year-old girl with language delay, hyperactivity and diminishing repetitive behaviors experienced difficulty completing classwork. Neurologist diagnosed ADHD with language delay. NP assessment revealed deficits in language, motor, and social interaction, but normal academic skills. Both children met criteria for ASD. Results: Case A: Testing revealed superior intellect, above-average academic skills, and mild but wide-spread social deficits. Child was placed in a mainstream class with Autism-related services. Case B: She scored well on early-reading and math tasks but IQ score was low due to hyperactivity and poor social interaction. She qualified for Autism-related services to support her development. Conclusion(s): NP assessment is critical for ASD diagnosis and selection of services. Neuropsychologists can elicit some symptoms and developmental strengths, which otherwise are not readily observed by teachers or pediatricians, to diagnose ASD and aide in educational planning.