Objectives: Coronary multi-detector computed tomography (MDCT) can evaluate coronary artery calcified and non-calcified plaque. The total amount of calcified plaques expressed as Agatston score is related with future events of coronary artery disease. However, it is not known for the usefulness of coronary artery calcium score at coronary stenotic lesion itself. We aimed to evaluate the impact of coronary artery lesion calcium score (CALS) measured by MDCT on stent expansion after drug-eluting stents (DES) implantation. Methods: We enrolled 44 lesions in 35 patients who were performed 64-slice coronary MDCT and treated by percutaneous coronary intervention (PCI). We measured the calcium score using Agatston method at coronary stenotic lesion (CALS) and entire coronary trees (total Agatston score). Intravascular ultrasound (IVUS) was performed at pre-PCI, after stent deployment and high pressure dilatation if performed. Stent expansion was assessed by post-stent minimal stent area (MSA) ���5.5 mm짼and divided the lesions into 2 groups according to above criteria, optimal (n=26) vs. non-optimal (n=18) groups. Results: Mean age was 63 짹 9 years old and 32 lesions were left anterior descending artery. There was no significant difference in diameter stenosis between two groups. However, the minimal luminal diameter (1.12 짹 0.37 vs. 0.90 짹 0.25 mm, p= 0.035) and reference vessel diameter (3.54 짹 0.41 vs. 3.29 짹 0.30 mm, p= 0.028) were higher in optimal group. Coronary MDCT and IVUS results have showed that CALS was well correlated with post-stent MSA (r= -0.358, p= 0.017). Total Agatston calcium score (394.9 짹 405.6 vs. 161.8 짹 206.0, p= 0.016) and CALS (123.1 짹 116.7 vs. 31.7 짹 47.3, p= 0.001) were significantly higher in non-optimal group. On multivariate analysis, CALS (odds ratio [OR] = 1.022, p= 0.004), stent diameter (OR= 0.018, p= 0.014), stent length (OR= 1.154, p= 0.047) were independent predictors for optimal stent expansion while total Agatston calcium score was not. Conclusion: The coronary lesion calcium score estimated by MDCT which represents regional calcium extent is useful parameter to predict optimal stent expansion after DES implantation.