A 47-year-old man had nasopharyngeal carcinoma (NPC). He received radiotherapy 10 years ago and was cancer-free after the treatment. However, diplopia occurred 1 year ago and became more progressive recently. An FDG-PET scan was performed to rule out the possibility of recurrence. No abnormal FDG uptake was demonstrated in the head and neck. However, an irregular area of increased FDG uptake was noted in the right lower lung. The plain chest x-ray showed barium retention in the same area, which might have resulted from aspiration of barium during gastrointestinal barium examination 2 years ago. A follow-up chest x-ray showed no apparent change and there was no evidence of metastases in the lung 6 months later.