The purpose of this study was to systemically review the available literature regarding the diagnostic performance of positron emission tomography (PET) using 2-[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) in patients with thymic epithelial tumors. We reviewed 13 studies that evaluated the diagnostic role of thymic epithelial tumors with [18F]FDG-PET. [18F]FDG-PET is a useful radiological modality for differentiating between thymomas and thymic carcinoma. However, [18F]FDG-PET may not be useful for differentiating low-risk thymoma and high-risk thymoma. One paper reported that [18F]FDG-PET has a predictive significance for treatment and prognosis in thymic epithelial tumors. Two papers reported that the degree of [18F]FDG uptake in thymic epithelial tumors is based on glucose metabolism. [18F]FDG-PET may have a further use for radiological differential diagnosis of thymomas and thymic carcinomas.