Background: Hypertriglyceridemia(highTG) is associated with small dense LDL particle formation and low level of HDL. Omega-3 fatty acids reduces hyperglycemia and is beneficial for prevention of post-myocardial infarct cardiovascular events. It also reported that it decreases inflammation at carotid plaque in patients with carotid stenosis. But, we do not know that reduction of inflammation by omega-3 fatty acid is limited to local vascular plaque or extended to whole body tissues including reticuloendothelial system in patients with highTG Purpose of the study: We would like to know whether reduction of inflammation by omega-3 fatty acid administration is limited to vascular tissue or extended to whole body tissues including reticuloendothelial system in patients with highTG. Methods: Using whole body combined fluorodeoxyglucose positron emission tomography/computed tomography imaging, we observed total 46 subjects consisted of highTG patients (n=21, 57짹12 years) and controls (n=25, 57짹8 years).To compare the local vascular plaque inflammation and systemic inflammatory RES activation, 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. We also measure repeated maximal SUV at same sites after omega-3 fatty acid 1.5 g for 6months. Results: The SUV of highTG patients in the carotid artery and ascending and descending aorta were significantly higher than controls. The SUV of highTG patients in the liver, spleen, bone marrow, lung and visceral fat were significantly higher than controls, 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=0.62 p<0.001) but neither vascular tissue nor RES SUV was associated with subcutaneous fat SUV. Omega-3 fatty acid administration for 6 months reduced both % decrease of max SUV of vascular plaque [ % decrease of max SUV=baseline max SUV-post Tx max SUV/ baseline max SUV X 100] (carotid: 24.9%, p<0.005; ascending aorta 18.67 %, p<0.001; descending aorta 20.13 %, p<0.001, respectively), and RES system(liver 34.8%, p<0.001; spleen 29.88%, p<0.001; bone marrow 10.14 %,p<0.001; lung 3.48 %, p<0.001: and visceral adipose tissue 5.38 %, p<0.001, respectively). Conclusion: These findings suggest that the administration of omega-3 fatty acid reduces inflammation not limited to local vascular tissue but generalized inflammatory organs in patients with hyper TGS.