Background and Objectives We have reported that the thickness of epicardial adipose tissue (EAT) by echocardiography was increased in patients with metabolic syndrome (MS). However, the impact of body mass index (BMI) has not been investigated. We hypothesized that the usefulness of EAT predicting MS might be affected by BMI. Methods We consecutively enrolled 643 patients (332 males, 59짹11 year-old), who underwent echocardiography for coronary angiography. EAT was measured on free wall of the right ventricle at end diastole in the parasternal window. MS was defined as NECP-ATP III guideline. All patients were divided into a group of BMI���27kg/m짼 (n=165) and <27kg/m짼 (n=478). Results Median and mean EAT of 643 patients were 3.0 and 3.1짹2.4mm, respectively. Mean EAT was significantly increased in patients with MS than those without MS (3.6짹2.5 mm, 2.5짹2.2 mm, respectively, p<0.001). When we analyze these patients according to BMI, mean EAT was not statistically increased in patients with MS in BMI���27kg/m짼group (Figure. Left panel). Receiver operating characteristic curve analysis predicting MS revealed that the area under curve of BMI���27kg/m짼 group was significantly lower than those of BMI<27kg/m짼(0.506 and 0.659, respectively, p=0.007, Figure. Right panels). Conclusions The power of EAT to predict MS was stronger in patients with BMI<27kg/m짼. These findings showed that the measurement of EAT thickness by echocardiography might be useful in patients with low BMI especially less than 27kg/m짼.