A 61-year-old man with previous history of lung adenocarcinoma underwent 2 18F-FDG PET/CT investigations. The first for assessment of enlarged mediastinal lymph nodes revealed an area of increased FDG uptake in the sigmoid colon (located at the right pelvis). Colonoscopy showed a segmental area of ischemic sigmoid colitis, confirmed on histology postbiopsy. The asymptomatic man had no risk factors, and no specific treatment was administered, apart from supportive measures. One year later, there was no significantly abnormal uptake on PET/CT. Incidental ischemic colitis may be demonstrated with FDG and PET/CT needing no specific therapeutic measures for resolution.