BACKGROUND: Positron Emission Tomography(PET) with [18F]-fluorodeoxyglucose (FDG) is a new imaging technique that has the advantage of imaging metabolic changes linked to malignancy. PET-FDG can provide a functional image of the regional biochemistry which may be more sensitive and accurate for detecting the presence of tumor in early stage. Recently, the clinical use of PET scan has been studied in many cancers but, there is a few clinical reports in oral and maxillofacial cancers. We have evaluated the ability of PET-FDG for initial diagnosis and detection of early subclinical recurrent malignancies in follow up check. PATIENTS AND METHODS: PET-FDG studies were performed in 33 patients from october, 1997 to september, 1998. 14 patients underwent PET-FDG evaluation for initial diagnosis and 19 patients for follow up check. RESULTS: Evaluated for initial diagnosis, PET-FDG was found to have an overall accuracy of 79%, sensitivity of 90%, specificity of 60%, positive predictive rate of 80% and negative predictive rate of 75%. Evaluated for follow up check, PET-FDG demonstrated accuracy of 84%, sensitivity of 91%, specificity of 75%, positive predictive rate of 83% and negative predictive rate of 86%. CONCLUSION: These data indicate that PET-FDG scan appears to be effective in initial diagnosis and detection of early recurrent oral and maxillofacial malignancies. The informations gained with PET-FDG can be included for essential treatment planning because of possibility of detection for early subclinical malignancies and distant metastases.