Diagnosis of vascular graft prosthesis infection is crucial, but not straightforward. Here we report two cases in which [(18)F] fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) was very useful in the diagnosis of aortic graft infection. Case 1: A 77-year-old Japanese man, two months status post aortic arch graft surgery, suffered from repeated fevers. Blood cultures revealed bacteremia. (18)F-FDG-PET/CT ruled out graft infection and diagnosed lumbar pyogenic spondylitis, which was treated with antibiotics, sparing the patient a possible reoperation. Case 2: A 53-year-old Japanese man, seven years status post replacement of the aortic root and ascending aorta, had been suffering from an ostensibly aseptic fistula for over a year and a half. Although repeated CT findings had been negative, (18)F-FDG-PET/CT clearly demonstrated communication between the fistula and the ascending aortic graft. He was treated with repeat ascending aortic replacement, omentopexy, and antibiotics. Our experience supports (18)F-FDG-PET/CT as a promising modality in cases of suspected vascular graft infection.