Summary:PET/CT imaging is most likely to be of use in radiation oncology with patients who have poorly defined target volume areas, e.g. brain tumours, bronchogenic carcinoma, and cases of miscellaneous geographical miss. Other tumours that call for dose escalated radiotherapy, such as head and neck tumours, bronchogenic carcinoma, and prostate carcinomas may further benefit from an accurate delineation of the metabolically active tumour volume and its differentiation from surrounding healthy tissue, or tumour atelectasis.