The value of QRS duration as a predictor of patients��� response to cardiac resychronization therapy (CRT) has been questioned. However, because measurements of mechanical dyssynchrony are still not validated, prolonged QRS remains a reasonable criteria for the selection of patients for CRT. In this study, we investigated the relationship of fQRS and dyssynchrony measured tissue Doppler image in patients with narrow QRS nonischemic dilated cardiomyopathy. We analyzed ECG of 64 subjects with dilated non-ischemic dilated cardiomyopathy who measured the synchrony index (Yu index) with tissue Doppler image. The subjects who have had ischemia pattern in past history and coronary angiography were excluded. DCMP was defined as LV end-diastolic dimension>55 mm with LVEF<45% on echocardiography and chronic mild to moderate HF (NYHA functional class II to III). The fQRS was defined by QRS<140ms and the presence of an additional R wave (R"), or notching in nadir of the S wave, notching of R wave, or the presence of more than one R prime (fragmentation) in two contiguous leads. Study subjects were divided into two groups according to the presence of fQRS. In 64 patients, fQRS was observed in 38 patients (59.4%) and the mean ejection fraction was 26.9%. The baseline characteristic was similar in both groups(Table 1). The synchronization index was significantly lower in fQRS group. There was a significant negative correlation between fQRS and dyssynchrony index(r = 0.32, p = 0.027) after adjustments for age, sex, EF, heart rate, QRS duration. fQRS is significantly correlated with dyssynchrony in patients with narrow QRS DCMP. Therefore, patients who have low EF and shorter QRS duration without fQRS can be candidates for CRT.