A 68-year-old man with sarcoidosis showed high F-FDG uptake in the mediastinal and hilar lymph nodes on F-FDG PET, suggesting active inflammation. F-fluoro-boronophenylalanine (FBPA) PET showed no significant uptake in the mediastinal and hilar lymph nodes, suggesting its cancer specificity as a substrate of L-type amino acid transporter 1. F-fluoro-boronophenylalanine PET can be used for precise evaluation in oncology when the differentiation between inflammation and metastasis is inconclusive on F-FDG PET.