INTRODUCTION: Diagnosis of Takayasu's arteritis as the cause of stroke is often delayed because of non-specific clinical presentation. F-18-fluorodeoxyglucose positron emission tomography-computed tomography may help to accurately diagnose and monitor Takayasu's arteritis in stroke patients. CASE PRESENTATION: We report the case of a left middle cerebral artery stroke in a 39-year-old man. Laboratory data were consistent with an inflammatory reaction. While abdominal contrast-enhanced computed tomography showed an aneurysm of the infrarenal aorta, only F-18-fluorodeoxyglucose positron emission tomography-computed tomography revealed pathology (that is, intense F-18-fluorodeoxyglucose accumulation) in the carotid arteries, ascending aorta and the abdominal aorta cranial to the aneurysm. After treatment with high-dose prednisone followed by cyclophosphamide, the signs of systemic inflammation decreased and F-18-fluorodeoxyglucose uptake was reduced as compared with the initial scan. CONCLUSION: F-18-fluorodeoxyglucose positron emission tomography-computed tomography showed inflammatory activity in the aorta and carotid arteries, suggestive of Takayasu's arteritis in a young stroke patient, and follow-up under immunosuppressive therapy indicated reduced F-18-fluorodeoxyglucose uptake. F-18-fluorodeoxyglucose positron emission tomography-computed tomography appears to be useful in detecting and quantifying the extent of vascular wall activity in systemic large-vessel vasculitis.