In this issue of PET Clinics, guest editors Drs. Stephen Hunt, Steven Feigenberg, and Charles B. Simone bring their considerable expertise to the topic of PET Applications in Radiation Oncology. PET imaging in radiation oncology provides valuable insights into tumor biology, treatment planning, and response assessment. As radiation therapy improves in precision and use, PET-based imaging modalities will become increasingly valuable in the design of radiation treatment fields. In this issue, top experts in the field discuss PET’s use in treatment planning, use in certain cancers, and use in reducing radiation-induced injuries.