FDG-PET (18-fluoro-desoxyglucose positron emission tomography) is a fonctionnal imaging method based on the high rate of glycolysis in different types of cancer-cells. We report the first five cases where FDG-PET was used in France for head and neck cancers. The results were analyzed on the basis of data reported to date in the literature, leading to a proposal for rational use of this diagnostic available in only a few centers in France. For primary assessment of cervicofacial carcinomas, different imaging techniques such as CT and MRI have improved tumor staging. Although 18-FDG-PET cannot replace these techniques used to monitor size and structural changes in tumors and lymph nodes, it will be helpful in following their metabolic activity. This diagnostic tool consequently is greatly helpful for detection and post-therapeutic evaluation of head and neck carcinomas and their recurrence. 18-FDG-PET is currently under evaluation as a tool for detecting cervical lymph nodes and early assessment of response to chemotherapy.