Presentation with a large mediastinal mass is a hallmark of acute lymphoblastic lymphoma, a disease that is treated in the same way as acute lymphoblastic leukemia even in the absence of marrow involvement. The role of mediastinal radiation for patients who achieve complete remission after chemotherapy has been overlooked and controversial. This document presents current knowledge on the role of radiation for lymphoblastic lymphoma and best practices for addressing how to deliver mediastinal radiation with modern technology.