This issue of PET Clinics focuses on Evolving Role of PET in Assessing the Efficacy of Immunotherapy and Radiation Therapy in Malignant Disorders, and is edited by Drs. Charles B. Simone II, Nicolas Aide, and Abass Alavi (the Consulting Editor of PET Clinics). Articles will include: The Value of PET Imaging to Guide Target Delineation for Radiation Oncology; PET Imaging to Determine Radiation Dose, Adapt Radiation Plans, and Predict Patterns of Failure and Overall Survival for Non-small Cell Lung Cancer; The Utility of PET/CT for Radiation Oncology Planning, Surveillance, and Prognosis Prediction for Gastrointestinal Tumors; Evolving Role of PET Based Novel Quantitative Techniques to Detect Radiation-induced Complications; Current and Future PET Based Quantitative techniques to Assess Response to Radiation Therapy; Diagnosis, Staging, Radiation Treatment Response Assessment, and Prognostication; FDG PET/CT for Assessing Tumour Response to Immunotherapy and Detecting Immune-related Side Effects: A Checklist for the PET Reader; PET Imaging with Therapeutic Antibody-based PD-1/PD-L1 Checkpoint Tracers; FDG PET/CT for Assessing Tumour Response to Immunotherapy in Lymphomas; FDG PET/CT for Assessing Tumour Response to Immunotherapy in Solid Tumours: Melanoma and Beyond; and more!