Background: Cardiovascular risk factors and cardiac structural changes associated with obesity/overweight are also major determinants of left ventricular (LV) diastolic function. Whether an increased body weight is associated with an impairment of LV diastolic mechanics, independent of associated risk factors, has not been fully established. The purpose of this study was to determine the effect of body weight on left ventricular diastolic function in Korean. Methods: Total 1280 subjects without structural heart disease or systolic dysfunction (LV ejection fraction < 50 %) were enrolled. The LV diastolic function was evaluated by traditional and tissue Doppler imaging. Peak early transmitral velocity (E), late transmitral velocity (A), and early diastolic mitral annulus velocity (E���) were measured, and E/A and E/E��� were calculated. The study subjects were divided into 3 groups: normal weight (body mass index [BMI] < 23.0 kg/m2), overweight (BMI 23.0 to 24.9 kg/m2), and obese (BMI���25 kg/m2). Results: Overweight and obese had lower E��� (both p<0.05) than normal weight subjects. The E/E��� ratio was higher in obese subjects than in normal weight subjects (p<0.05). In multivariate analyses, BMI was independently associated with higher A and E/E��� (both p<0.01). The risk of diastolic dysfunction was significantly higher in obese subjects (adjusted odds ratio: 1.594, 95% confidence interval: 1.134-2.240, p=0.007) compared to normal weight subjects, but not in overweight subjects (adjusted odds ratio: 1.127, 95% confidence interval: 0.775-1.637, p=0.531). Conclusion: Increased BMI was associated with impaired LV diastolic function independent of LV mass and associated risk factors. Obesity is an independent predictor of diastolic dysfunction. Therefore, therapeutic strategies aimed at promoting optimal body weight resulted in improvements in LV diastolic dysfunction.