Purpose: We evaluated the diagnostic accuracy of low dose coronary CT angiography (CCTA) with a 128-slice MDCT against a conventional coronary angiography (CCA) for the detection of significant stenosis (���50% lumen diameter narrowing). Materials and Methods: Thirty-six patients ( 25 male, 11 female, mean age: 59.7 짹 10.6 years) underwent a MDCT and a subsequent CCA to evaluate atypical chest pain (28 patients) or suspected coronary artery disease (8 patients). A MDCT angiography was performed with a 128-slice MDCT-scanner (Definition AS+, slice collimation 64��0.6 mm) using different two low dose techniques by heart rate (���step and shoot��� & ���Mindose���). The coronary artery segments were classified according to a 15-segment model. The sensitivity, specificity, positive predictive value and negative predictive value of the 128-slice MDCT for the detection or exclusion of significant CAD were calculated on a per-segment. Results: Thrity-five (97.2%) of the 36 coronary CT angiograms were of diagnostic image quality with 89.1% (468 of 525) of the coronary segments assessable by CT angiography. Eighty-seven (18.5%) segments showed significant stenosis by CCA. Stenosis of 50% or greater was detected by sensitivity, specificity, positive predictive value, and negative predictive value on a per segment basis (85.0%, 92.5%, 65.5%, 97.3%, respectively). Mean patients radiation dose was 3.57 짹 1.94 mSv Conclusion: Low dose coronary CT angiography (CCTA) with a 128-slice MDCT coronary angiography in the ���step and shoot��� & ���Mindose��� mode provides the high diagnostic accuracy for assessment of significant coronary stenoses at a low radiation dose.