For majority of lymphoma patients who relapse after complete response or who are primary refractory to initial treatment, a combination of salvage chemotherapy followed by high dose chemotherapy and ASCT is considered the standard of care. Sensitivity to salvage chemotherapy affects the outcome after ASCT. Traditionally, the response to salvage chemotherapy prior ASCT was determined by conventional computed tomography (CT) scans using size criteria. In the past several years, it has been shown that functional imaging with PET scans using fluorodeoxyglucose (FDG) provides additional information to anatomic imaging with CTs. Recently, PET scans have been incorporated into the response assessment as published by the Imaging Subcommittee of International Harmonization Project in Lymphoma. These days, most institutions use PET/CT scans which incorporate functional imaging with PET scan fused with low dose non-contrast enhanced CT scan.