OBJECTIVE: The goal of this study was to evaluate the usefulness of positron emission tomography with [(18)F]fluorodeoxyglucose ([(18)F]FDG-PET) in detecting metastases in patients with gestational trophoblastic tumor (GTTs). METHODS: A retrospective study was conducted on three patients with GTTs who had been studied with [(18)F]FDG-PET and computed tomography (CT) after an increase in human chorionic beta-gonadotropin (betahCG) serum levels. PET scans were performed with a multiring whole-body positron emission tomograph 45 min after an intravenous bolus injection of [(18)F]FDG ( approximately 5.2 MBq/kg). CT studies were obtained on a spiral scanner prior and after administration of intravenous iodinated contrast material. Within a week of CT and [(18)F]FDG-PET studies, the patients underwent surgical procedures for histological diagnosis. RESULTS: In one patient, a lung lesion positive for neoplastic tissue with [(18)F]FDG-PET and negative with CT was confirmed to be a GTT metastasis at histology. In another patient, [(18)F]FDG-PET was negative, while CT was positive for the presence of lung metastasis; no viable tumor tissue was found at histological analysis. The remaining patient had a positive [(18)F]FDG-PET and CT study for lung metastasis; this was confirmed at histological analysis. In the same patient, both [(18)F]FDG-PET and CT depicted the presence of a liver lesion. Necrotic lesion regression after treatment was clearly documented with [(18)F]FDG-PET only. CONCLUSIONS: Our preliminary results suggest that [(18)F]FDG-PET may be useful for the assessment of metastatic disease in patients with GTTs.