The greatest challenge for radiation therapy is to attain the highest probability of cure with the least morbidity. Implementation of conformal radiotherapy techniques offers the possibility to target irregularly shaped volumes while optimally sparing the normal tissues. This implies however an accurate knowledge of the exact tumour extension. In order to perfectly delineate the primary tumour and to optimise the radiation dose administered to normal tissues, it is necessary for patients to undergo imaging studies. Both anatomical and functional imaging studies are currently being evaluated for treatment planning of head and neck cancer.