Positron emission tomography (PET) has obtained a place in the management of patients with hematologic disease particularly those with lymphoproliferative disorders. In the staging and monitoring of cancer, the use of PET in combination with fluorine-18 fluorodeoxyglucose (FDG) has already demonstrated its benefit when compared with conventional imaging modalities. One such area which has already profited from the use of PET is Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). Computed tomography and magnetic resonance imaging are equivalent in staging and monitoring disease, while gallium-67 imaging is more useful in HD and high grade NHL for studies of response to therapy.Paul et al. in 1987 were the first to describe PET imaging in patients with lymphoma; since this time a number of studies have demonstrated that PET technique is superior to 67 Ga imaging in staging lymphoma before therapy and is useful in the evaluation and the prediction of relapse after high dose therapy with stem cell transplantation.PET is based on the utilisation of positron emitting radiopharmaceuticals and the detection in coincidence of the two nearly collinear 511-keV photons emitted following positron annihilation with an electron in vivo. By surrounding the patients with detectors, a large number of acquired coincident events can lead to the construction of an image of the in vivo radioisotope distribution.