A 26-year-old man had unilateral facial numbness. A brain MRI suggested possible brain metastases. 18F-FDG and 11C-choline PET/CT revealed multiple sites of abnormal activity in the body. However, 11C-choline PET/CT was more impressive than FDG PET/CT. Especially, the brain lesions revealed by MRI had only elevated 11C-choline uptake but had FDG uptake levels similar to adjacent brain. Acute myeloid leukemia was diagnosed after bone marrow biopsy.