A 68-year-old man was hospitalized for unstable angina and underwent emergency coronary artery bypass surgery. During the operation, a pulsatile large abdominal aortic aneurysm (AAA) was discovered. To define the optimal treatment of the abdominal aneurysm, after bypass surgery, CT scans and positron emission tomography (PET) were performed, as we routinely do. PET imaging combined with immunohistologic examination showed a region of increased F-18 FDG uptake corresponding to an inflammatory infiltrate in the aortic wall in contrast to the thrombus in the aneurysm (devoid of inflammatory cells). The luminal area showed midlevel F-18 FDG uptake corresponding to circulating mediators.