BACKGROUND: Although 18 F-FDG-PET/CT is a widely used diagnostic tool for several malignancies, its efficacy in diagnosing pancreatic neuroendocrine tumors is reported to be controversial because of the short-term follow-up. METHODS: We retrospectively compared demographics and pathological features between 18 F-FDG-positive and -negative diseases. Additionally, we evaluated whether the avidity of 18 F-FDG-PET/CT affected earlier recurrence after curative treatment of non-functioning tumors. The median duration of observation was 65.6 months. RESULTS: Seventy-two patients were enrolled. 18 F-FDG-positive diseases were pathologically advanced and significantly associated with metastatic behavior. In a multivariate analysis, metastatic behavior and WHO tumor grade was independently associated with 18 F-FDG accumulation. Only 25% of functional tumors (4/16) and 8% of insulinomas (1/12) were 18 F-FDG-positive. In a Kaplan-Meier analysis in patients with non-functioning tumors (n = 56), 18 F-FDG-positivity was significantly correlated with poorer recurrence-free survival (RFS) but had no correlation with overall survival. In univariate analysis of factors associated with shorter RFS, male gender, prevalence of nodal metastasis, WHO tumor grade ≥G2, or 18 F-FDG-positive disease were significantly higher in patients with shorter RFS, whereas only 18 F-FDG-positivity was associated with shorter RFS in multivariate analyses. CONCLUSIONS: The avidity of 18 F-FDG-PET/CT was associated with metastatic behavior of pancreatic neuroendocrine tumors and recurrence after treatment of non-functioning tumors.