Objective: Precise delineation of meningiomas is difficult on CT and MRI especially at the skull base and regarding invasion of bone, dura or the pituitary gland. The aim of this study was to explore the diagnostic potential of 18F-FET PET. Design: Prospective study. Methods: Total 24 patients with suspected meningioma on MRI/CT had additional dynamic 18F-FET PET before surgery. Regions of interest (ROI) were defined in the tumor and critical structures in the skull base. Standardized uptake values (SUV) and tumor-tissue ratios (T/Tis) were determined. Time activity curves (TAC) in the tumors were analyzed and compared with histological data. Results: FET uptake differentiated tumor from critical tissues. A T/Tis > 1.2 ratio differentiated meningioma tissue from the brain/periorbita/tentorium and bone in 100% of patients, from pituitary and dura in 96%, from mucosa in 88%, and from cavernous sinus in 71% of patients. Late FET uptake was significantly lower in meningiomas of WHO grade I than in meningiomas of WHO grade II or III. Two TAC patterns of FET-PET uptake were observed. Combination of SUV (cutoff, 2.6) and TAC pattern allowed the differentiation of high grade and low-grade meningiomas with a sensitivity of 85% and specificity of 100%. Conclusions: 18F-FET PET may contribute to delineation of meningiomas in critical anatomical regions at the skull base; moreover, it may be helpful for preoperative WHO grading.