PURPOSE: The aim of this study was to test the usefulness of real time 3D echocardiography(RT3D) for assessment of ventricular dyssynchrony. METHOD: Regional 3D volume and TDI were estimated in 18 patient (age 58.6짹12.8, M: F =11:7, EF 15%~67%, QRS duration 80~190ms). 3D volume of 16 LV segments by American society of echocardiogrphy was recorded by Sonos 7500 Live 3D system and was analyzed using TomTec software in off-line. Time to peak regional volume changes(Tv) by RT3D and time to peak sustained systolic contraction(Ts) by TDI were measured and the standard deviation of Tv(Tv-SD) and Ts(Ts-SD) were used as parameters of the time domain dispersion. Volume curves of each segment were synchronized by arranging the point of peak volume change to the same point of the cardiac cycle(Figure). Net gain of ejection fraction (EF-gain) by virtual resynchronization was used as a new index of the volume domain dispersion. The relations between Tv-SD, EF-gain by virtual resynchronization, Ts-SD in the same segment and QRS duration were compared. RESULTS : 1. Tv-SD was closely related to Ts-SD(r=0.637, p=0.004). 2. EF-gain by virtual resynchronization was closely related to Ts-SD (r=0.587, p= 0.011) 3.Ts-SD(r=0.244, p=0.377) and Ts SD(r=0.182, p=0.470) were not related to QRS duration. CONCLUSION: Dispersion of regional volum change and EF-gain by virtual resynchronizaton using RT3D might be a promising parameter that can predict the response of CRT.