Backgrounds: Because the rupture of vulnerable atherosclerotic plaque is one of the most important etiologies of acute coronary syndrome(ACS), its early detection is clinically important. The aim of this study was to elucidate whether ¹⁸F-FDG carotid PET CT and carotid ultrasound can predict acute inflammation suggesting vulnerable plaque in ACS.Methods: 17 patients (M:F=11:6,mean age=59짹11yrs)underwent coronary angiogram were divided into two groups[non-ACS(8 pts) and ACS Group(9 pts)].¹⁸F-FDG carotid PET/CT(Fig A) and carotid ultrasound(Fig B) were performed in all patients. The maximal and mean standardized uptake value (SUV) on 60 and 180 min delayed images in carotid PET/CT were compared with serum inflammatory markers,lipid profile and presence of carotid plaque in both group. Results:1.There was a significant correlation between right mean SUV and hs CRP (r=0.53, p=0.04)(Fig C). 2.Right mean SUV was significantly higher in 7 patient with echolucent plaque in carotid ultrasound (echolucent vs non-echolucent plaque=1.4짹0.1 vs 1.2짹0.2,p=0.03) 3.HDL level had a negative correlation with mean SUV in 60 and 180 min-delayed images respectively. (right, r=-0.60, p=0.01/r=-0.716, p=0.03) (left, r=-0.74, p=0.03 /r=-0.64, p=0.01).Conclusion: Our results show that ¹⁸F-FDG carotid PET/CT can depict metabolically active atherosclerotic plaques. Therefore, ¹⁸F-FDG carotid PET/CT could be used as a noninvasive imaging modality for the early detection and monitoring of ACS