Abstract: PET-CT is a dual-modality imaging tool and has a major role in malignant tumors. The CT antoraic data and metabolic ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET data can be obtained with PET-CT scanner in a single study. The fusion imaging of antomic data and metabolic data provides valuable information to help the precise location of disease and to some extent avoid potential pitfalls. ¹⁸F-FDG is a glucose analogue and may markedly accumulate in lymphoma cells. ¹⁸F-FDGPET-CT plays a very important role in the detection and staging of lymphoma, restaging after treatment, monitoring treatment response and radiotherapy planning, but isn't a substitute of biopsy.