Background: Stent material and thickness might be a key determinants to restenosis even in a drug eluting stent era. Thin strut cobalt chromium stent has been developed in an attempt to reduce a restenosis rate and maintain radiopacity and radial strength. Objective: The purpose of this study is to compare the Stainless Steel Core 짰stent (thickness: 90 micrometer/ HUMED Co. Ltd, Korea) and Cobalt-Chromium Core짰 stent (thickness: 60 micrometer/ HUMED Co. Ltd, Korea) in a porcine coronary stent restenosis model. Methods: We implanted the Cobalt-Chromium (CC) stent and the Stainless Steel (SS) stent in 24 coronary arteries. Four weeks after implantation, pigs were sacrificed after coronary angiography. The coronaries were perfusion-fixed and stained, and pathologic examination was performed by computer-aided histomorphometry (SigmaScan Pro 5.0, Jandel Co., USA). Results: 1)The minimal luminal diameter at 4 weeks was larger in the CC stent group than SS stent group in coronary angiography (1.8 짹 0.8 mm Vs 2.7 짹 0.8, p=0.010). 2)The neointimal area was significantly smaller in the CC stent than the SS stent group (1.96 짹 0.68 mm2 Vs 0.89 짹 0.27 mm2, p=0.00005) 3)The intima /media area ratio was significant lower in the CC stent than the SS stent group (1.33 짹 0.46 Vs 0.80 짹 0.29, p=0.025) Conclusions: Thin strut cobalt chromium alloy stent reduced a neointimal formation significantly compared to stainless steel stent in a porcine coronary stent injury model.