A 79-year-old man was hospitalized because of a chest X-ray abnormality. The chest X-ray film revealed infiltration in the left middle lung field. Chest CT scan showed mediastinal lymphadenopathy, and consolidated opacities with ground-glass opacities in the S3 and a part of the S3 segments of the left upper lobe. CT-guided needle biopsy demonstrated caseating epithelioid granuloma with multinucleated giant cells. 18F-fluorodeoxyglucosepositron emission tomography (FDG-PET) showed intense uptake (standardized uptake value (SUV) max 1 hour/2 hours 18.0/21.8) in the left upper lobe. Bronchial lavage fluid culture revealed Mycobacterium tuberculosis. From these findings, we made a diagnosis of caseous pneumonia with intense uptake on FDG-PET. After antituberculosis therapy, chest X-ray images and a CT scan showed improvement of the consolidation, the ground-glass opacities and mediastinal lymphadenopathy. Intense FDG uptake in caseous pneumonia may represent its high activity. This is the first reported case of caseous pneumonia examined by FDG-PET in Japan.