BACKGROUNDS Epicardial fat thickness has been known to be associated with metabolic disorder such as metabolic syndrome and obesity. Also, the metabolic disorder is associated with atrial dilation and diastolic dysfunction although the causative mechanisms are not completely understood. We hypothesized that forces extrinsic to the myocardium may contribute to diastolic dysfunction in this setting. Therefore, we sought to evaluate the association between epicardial fat and diastolic dysfunction. METHODS The study was performed in 151 patients with normal systolic function. Patients with significant arrhythmia, left ventricular hypertrophy, significant valvular disease, and coronary artery disease were excluded. The epicardial fat thickness on the free wall of the right ventricle was measured at end-diastole from the parasternal long-axis views of 3 cardiac cycles. Diastolic function was evaluated using the mitral inflow (early (E) and late (A) and mitral ratio (E/A ratio), deceleration time (DT)), and mitral annular tissue-Doppler imaging (TDI) parameters (early(E���) and late (A���) and E/E���). RESULTS 151 patients ( 57.2짹12.9 years, 0.41짹0.2 mm fat thickness ) were divided into 2 groups ( 30 patients with normal vs. 121 patients with abnormal mitral inflow pattern). There were significant differences in age, and fat thickness (0.27짹0.12 mm vs. 0.44짹0.2 mm)(p<0.001). The patients with a higher epicardial fat thickness were associated with a high E/E��� (p<0.01). Multivariate analysis showed that epicardial fat thickness (OR 3.44, p=0.011), age (OR 0.096, p=0.001), DM (OR 1.369, p=0.032) were an significant predicting factor for the E/E���, whereas clinical parameters such as sex, hypertension, metabolic syndrome, and BMI had no statistical significance. CONCLUSIONS This study showed that an increase in epicardial fat thickness is more directly related with impairments in diastolic function rather than metabolic disorders.