Differential Diagnosis of Autism Spectrum Disorder provides a framework for clinical considerations and best practices related to diagnosing children with autism spectrum disorder (ASD) versus commonly co-occurring conditions. Differential diagnosis is a complex process, and it is common for clinicians to observe symptom overlap between conditions. In this comprehensive text, the authors focus on the similarities and differences between ASD and a second diagnosis. Leading experts provide practical guidance in the diagnostic process for ASD versus a second condition, such as anxiety or attention deficit/hyperactivity disorder. Each chapter includes clinical case studies to provide real-world examples of how clinicians make diagnostic decisions. Ample illustrations and ’decision trees’ provide a visual representation of clinical decision-making.