Takayasu arteritis (TA) and ulcerative colitis (UC), both immune-mediated inflammatory diseases, rarely occur together. This report describes TA in a 29-year old female patient who was being treated for UC for three years. As she had left-side neck pain and headache, she was diagnosed with TA and her response to tumor necrosis factor (TNF) inhibitor was assessed by fluorine-18-fluorodeoxyglucose ( 18 F-FDG) positron emission tomography (PET)/computed tomography (CT). Positive responses to the TNF inhibitor were seen by PET/CT for the TA and by endoscopy for the UC. We conclude that TNF inhibitors are effective treatments for both TA and UC. We found that PET/CT is a useful for diagnosing and assessing TA. (J Rheum Dis 2017;24:55-59)