Background: Routine adjunctive balloon post-dilation (ABP) following drug-eluting stent (DES) implantation in coronary true bifurcation lesion may adversely impact on side branch patency. This study aimed to determine the impact of ABP in main branch following DES implantation on mid-term angiographic and clinical outcomes in the treatment of coronary bifurcation lesion. Methods: A total of 730 consecutive patients (pts) with coronary bifurcation lesion treated with DES were enrolled. Study population was divided into the ABP group and the no ABP group. Six-month angiographic and 1 year clinical outcomes were compared between the two groups. Results: Baseline clinical and procedural characteristics were similar between the groups, except larger reference diameter (3.02짹0.46 vs. 2.90짹0.47, P=0.002) and stent diameter (3.03짹0.39 vs. 2.95짹0.39, P=0.008), longer stent length (25.57짹5.83 vs. 24.31짹6.41, P=0.009) and less stent number/pt (1.68짹0.99 vs. 1.88짹1.07, P=0.011) in the ABP group. Immediate post intervention minimal luminal diameter (MLD, 2.97짹0.55 vs. 2.82짹0.52, P=0.001) and acute gain were larger in the ABP group. The incidence of angiographic side branch jailing was higher in the ABP group. However, angiographic outcomes at 6 months and major clinical outcomes up to one year were not different between the two groups (table). Conclusions: Routine ABP after DES implantation in true coronary bifurcation lesion did not impact on overall midterm angiographic and clinical outcomes.