Background The mechanisms responsible for the occurrence of a kissing unsatisfied (KUS) result after classical crush stenting remain unclear. The present study aimed at analyzing the mechanisms and clinical significance of KUS. Methods Two hundred and thirteen patients with true bifurcation lesions treated with classical crush stenting and final kissing balloon inflation (FKBI) were assigned to upper, middle, and lower groups according to the position of the side branch re-wiring assessed by visual estimation, quantitative coronary analysis (QCA) and intravascular ultrasound (IVUS). Angiographic follow-up was indexed at 12 months.Results The upper group was characterized by a larger bifurcation angle of 55.53°±95.25° (P=0.030) and a longer procedural time (42.43±93.92) minutes (P=0.015). The overall rate of KUS by visual estimation was 10.48%, with 5.4% in the upper group, 3.9% in middle group, and 36.1% in lower group (P <0.001). For the diagnosis of KUS, visual inspection demonstrated a good correlation with both QCA and IVUS. Smaller stent diameter was the main reason for KUS in the upper group, while extra-stent side wire location, or re-wire in a low position was the main mechanism attributed to KUS in the lower group. The Lower group had more restenosis, with most restenotic lesions at a lower position of the side branch ostium. KUS (HR 1.652, 95% Cl 1.332-2.088, P <0.001) and re-wiring position (HR 2.341, 95% Cl 1.780-4.329, P <0.001) were two independent predictors of side branch restenosis. Re-wiring position (OR 0.458, 95%Cl 0.336-0.874, P=0.001) and side stent expansion (OR 3.122, 95%Cl 2.883-5.061, P=0.014) were factors predicting the findings of KUS.Conclusions Side wire outside side stents resulted in more KUS and restenosis. Different restenotic lesion types reflected individual mechanisms contributing to the development of plaque proliferation.