Positron emission tomography (PET) could have a number of potential advantages in refining and improving the management of patients with PCNSL. Because of the rare incidence of PCNSL, the value of PET has however not been well defined in this subtype of lymphomas. There are a few studies that have investigated the role for FDG-PET and amino acid PET in the primary staging/diagnosis and response assessment in PCNSL patients, but the results are inconclusive. Further studies are therefore needed.