A 48-year-old man with progressive respiratory symptoms was suspected of having relapsing polychondritis (RPC). A 99mTc-MDP bone scintigraphy showed only mild activity in the bilateral costal cartilage. In contrast, 18F-fluoride PET/CT revealed intense radioactivity accumulation in the tracheal cartilages. Biopsy results from tracheal cartilage were consistent with a diagnosis of RPC. The patient received therapy toward RPC, and his symptoms was gradually alleviated.