Background: Stent strut metal induced blooming artifact makes difficult to quantitative coronary analysis by MDCT. There is a little data on the efficacy of using 64 detector MDCT in evaluating coronary stent luminal dimensions. The objective of this study is to determine the utility of multislice computed tomography (MDCT) technology to evaluate coronary stent luminal diameter. Methods: Six coronary stents (3.0��28 mm Cypher, 3.0��28mm Taxus liberte, 3.0��28mm Endeavor, 3.0��30mm Crossflex, 3.0mm��15mm Mincrown, and 3.0��19mm Jo stent) were deployed in silicone tubes(inner diameter of 3mm) and tubes were filled with diluted contrast (1:20 dilution of Ultravist). The tubes were scanned with 64-slice MDCT at 120kVp. The strut thickness was measured by MDCT and in-stent luminal diameter (ISLD) measured by MDCT compared to intravascular ultrasound (IVUS). Results: Stent strut thickness(mm) was different among stent type(Cypher 1.30짹0.00, Taxus liberte 0.95짹0.05, Endeavor 1.02짹0.08, Crossflex 1.12짹0.04, Mincrown 1.22짹0.04, Jo stent 1.15짹0.14, p<0.01). ISLD determined by 64 MSCT vs. IVUS is: (Cypher 2.89짹0.03 vs 1.70짹0.19, Taxus liberte 2.88짹0.05 vs 1.98짹0.10, Endeavor 2.95짹0.02 vs 1.91짹0.09, Crossflex 2.85짹0.03 vs 1.68짹0.31, Mincrown 2.74짹0.02 vs 1.38짹0.17, Jo stent 2.88짹0.08 vs 1.78짹0.18, p<0.01). Conclusion: MDCT measurement results in a significant underestimation of ISLD by compafision of IVUS measurement. This lumen underestimation by artifact limits the applicability of CT angiography to quantify in-stent luminal reserve. Further development of technique for decrease artifact would be necessary.