Background: Metabolic syndrome(MS) is associated with visceral fat inflammation. And metabolic syndrome is also associated with high prevalence of coronary artery disease. We do not know that inflammation is limited to local visceral adipose tissues or prevailing to whole body tissues in patients with metabolic syndrome. Liver, spleen and bone marrow represent the organs with high reticuloendothelial system (RES) activity. This system is composed of cells which play an active role in the defense mechanism. We hypothesized that in patients with MS, metabolic activity of organs containing both visceral adipose tissue and RES will be higher than control subjects. Purpose of the study: We would like to know whether inflammation is limited to visceral adipose tissue or associated with systemic activation of RES in patients with MS. Methods: Using whole body combined fluorodeoxyglucose positron emission tomography/computed tomography imaging, we observed total 57 subjects consisted of MS patients (n=32, 57짹12 years) and controls (n=25, 57짹8 years). Maximal standard uptake value (SUV) of the highest regions of interest was calculated in the vascular tissues such as right carotid artery, ascending and descending aorta, and RES system such as liver, spleen, bone marrow, lung and visceral fat. Results: The SUV of MS patients in the carotid artery and ascending and descending aorta were significantly higher than controls (MS vs. controls; carotid artery: 2.02 짹 0.03 vs. 1.22 짹0.15, p<0.001; ascending aorta 1.92 짹 0.26 vs 1..17 짹 0.09, p<0.001; descending aorta 1.88 짹 0.06 vs 1.17 짹 0.21, p<0.001). The SUV of MS patients in the liver, spleen, bone marrow, lung and and visceral fat. was significantly higher than controls (MS vs. controls; liver: 3.18짹0.74 vs 1.57 짹 0.85 , p<0.001; spleen 2.56 짹 0.63 vs 1.72 짹 0.41, p<0.001; bone marrow 2.71 짹 0.15 vs 1.15 짹 0.52, p<0.001; lung 0.63 짹 0.67 vs 0.05 짹 0.79, p<0.001: visceral fat: 1.67 짹 0. 51 vs. 0.12 짹 0.13, p<0.001), whereas subcutaneous fat SUV were not significantly different among groups. The SUV of vascular tissue and RES system and that of visceral adipose tissue were significantly correlated (rho=0.71, p<0.001) but neither vascular tissue nor RES SUV was associated with subcu-fat SUV. Conclusion: These findings suggest that the inflammation is not limited to local visceral adipose tissue but prevailed over whole RES system in patients with MS. This could imply that organs with RES cells play an important role in the inflammatory response which can be detected and quantified by the FDG-PET imaging technique. The degree of this response may have a prognostic role in such patients and should be explored further in the future.