Background: The aim of this study was to assess the impact of stent geometry on in-stent neointimal hyperplasia and regional persistent remodeling after sirolimus-eluting stent (SES) implantation. Methods: Intravascular ultrasound (IVUS) interrogations at 6.5 짹 1.3 months after SES implantation were performed in 53 stents in 44 patients. In all stents, cross-sectional measurements were performed at 1-mm interval. Symmetry index (SI) was calculated as minimum / maximum stent dimension ratio. Asymmetry and underexpansion were defined as SI < 0.8 and stent area (SA) < 5 mm2, respectively. In each lesions and stents, most asymmetric and underexpanded sections were selected. Mean reference area (MRA), external elastic membrane area (EEMA), SA, lumen area and percent in-stent neointimal hyperplasia area (% NIHA) were measured and compared between each two groups. Additionally, sixty-four corresponding image slices on post implantation and follow-up IVUS studies of 16 stents were acquired. Percent ��EEMA, ��EEM radii at minimal and maxmial stent radii protion were measured after identification of geometric center. Results: At follow-up, % NIHA of asymmetry (n=21, 8.73짹4.32%) and underexpansion (n=15, 8.84 짹 6.72%) groups were not greater than that of symmetry (n=32, 6.84 짹 5.09 %) (p=0.168) and full-expansion (n=38, 8.17짹 6.06%) (p=0.780) groups. But SA/MRA was decreased in underexpansion group (0.69짹0.09) compared with full-expansion group (0.81짹0.12) (p=0.034). In addition, %��EEMA were greater in asymmetry group (16.9짹6.9%) compared with symmetry group (9.8짹4.1%) (p=0.028). ��EEM radii at minimal stent radii portion (0.19짹0.12 mm) were greater than that at maximal stent radii portion (0.05짹0.04 mm) (p=0.045). Conclusion: Stent asymmetry and underexpansion were not associated with increase of in-stent neointimal hyperplasia. But underexpansion was associated with decreased SA/MRA and asymmetry was associated with regional peristent remodeling after SES implantation.