Cancers of the head and neck account for more than half a million cases worldwide annually, with a significant majority diagnosed as squamous cell carcinoma(HNSCC). Imaging studies such as contrast-enhanced computed tomography(CT), magnetic resonance imaging(MRI) and ~(18)F-2-fluoro-2-deoxy-D-glucose positron-emission tomography/computed tomography(~(18)F-FDG PET/CT) are widely used to determine the presence and extent of tumors and metastatic disease, both before and after treatment. Advances in PET/CT imaging have allowed it to emerge as a superior imaging modality compared to both CT and MRI, especially in detection of carcinoma of unknown primary, cervical lymph node metastasis, distant metastasis, residual/recurrent cancer and second primary tumors, often leading to alteration in management. PET/CT biomarker may further provide an overall assessment of tumor aggressiveness with prognostic implications. As new developments emerged leading to better understanding and use of PET/CT in head and neck oncology, the aim of this article is to review the roles of PET/CT in both pre- and post-treatment management of HNSCC and PET-derived parameters as prognostic indicators. Cancers of the head and neck account for more than half a million cases worldwide annually, with a significant majority diagnosed as squamous cell carcinoma (HNSCC). Imaging studies such as contrast-enhanced computed tomography (CT), magnetic resonance imaging (MRI) and ~ (18) F-2-fluoro-2-deoxy-D-glucose positron-emission tomography / computed tomography (~ (18) F- FDG PET / CT) are widely used to determine the presence and extent of tumors and metastatic disease , both before and after treatment. Advances in PET / CT imaging have allowed it to emerge as a superior imaging modality compared to both CT and MRI, especially in detection of carcinoma of unknown primary, cervical lymph node metastasis, distant metastasis, residual / recurrent cancer and second primary tumors, often leading to alteration in management. PET / CT biomarker may further provide an overall assessment of tumor aggressiveness with prognostic implications. n head and neck oncology, the aim of this article is to review the roles of PET / CT in both pre- and post-treatment management of HNSCC and PET-derived parameters as prognostic indicators.