Background: Some autopsy studies showed a greater atherosclerotic plaque burden at the low shear stress regions of bifurcation. But there has been few clinical studies observing the plaque distribution in the bifurcation lesions. We wanted to analyze the plaque and neointimal distribution in the bifurcation lesions in the relation to shear stress distribution, in the in-stent restenosis (ISR) region as well as in the native coronary arteries. Methods: We examined native coronary artery bifurcation lesions (group 1, N=16) and 9-month follow-up stented bifurcations treated with T-stenting technique (group 2, N=18) using volumetric IVUS analysis for both main vessel (MV) and side branch (SB). Three 5-mm interested segments were analyzed; parent vessel ostium (PVo), main branch ostium (MBo) and side branch ostium (SBo). At each segment, four-quadrant (divided according to the takeoff of the side branch and the geometric center of the lumen) analysis was performed; carinal, abcarinal, myocardial, and epicardial. Eccentricity index was defined as the ratio of abcarinal and carinal plaque or neointimal volume. Results: In group 1, there was a significant difference of the plaque distribution among the four quadrants, the most in the abcarinal quadrant and the least in the carinal quadrant. While in group 2, there was no difference of the distribution of the neointimal volumes among 4 quadrants. The eccentricity index were significantly higher in group 1 than group 2 (4.5짹3.8 vs 3.3짹6.0, p<0.0001). Conclusion: Plaque burden was higher in the abcarinal quadrants in native coronary bifurcations lesion, but not in instent restenosis lesions. Perhaps native plaque or neointimal formation seems to follow the shear stress distribution in native artery, but in instent restenosis in coronary bifurcation.