In the present review, the authors report the published evidence on the use of functional imaging with FDG-PET/CT in assessing the final response to treatment in Hodgkin lymphoma. Despite a very high overall Negative Predictive Value of post-chemotherapy PET on treatment outcome ranging from 94% to 86%, according to different treatment intensity, the Positive Predicting Value proved much lower (40–25%). In the present review the Authors discuss the role of PET to guide consolidation RT over a RM after different chemotherapy regimens, both in early and in advanced-stage disease. A particular emphasis is dedicated to the peculiar issue of the qualitative versus semi-quantitative methods for End-of Therapy PET scan interpretation. A short hint will be given on the role of FDG-PET to assess the treatment outcome after immune checkpoint inhibitors.