Positron emission tomography (PET) has been shown to be effective in detecting intracranial malignancies based on cerebral glucose metabolism. To evaluate the ability of PET to detect extracranial head and neck neoplasms and cervical metastases, 16 patients with primary squamous cell carcinomas were examined. All patients received preoperative computerized tomography (CT) and magnetic resonance imaging (MRI) scans and underwent PET evaluation using intravenous 18F-2-fluoro-2-deoxy-D-glucose (FDG). Histopathologic analysis compared tumor invasion and positive lymph nodes with findings on MRI, CT, and PET images. All primary tumors were delineated by PET, while MRI and CT failed to detect one superficial tumor involving the anterior tongue. Ten nodes were detected by CT and MRI versus 12 nodes demonstrated by PET. PET is highly effective in detecting head and neck carcinomas as well as metastatic cervical lymph nodes. In addition, PET may be useful in evaluating postsurgery and postradiotherapy patients for recurrent and new primary tumors.