Backgrounds : To compare the diagnostic accuracy of ECG-gated 64-MDCT coronary angiography between sublingual nitroglycerin (NTG)-receiving group and non-receiving group. Subjects and methods : Between December 2006 and March 2007, 65 patients (M : F = 34 :31, mean age=61.6짹9.4) with suspected coronary artery disease underwent ECG-gated 64-MDCT coronary angiography (CTCA) and conventional coronary angiography (CAG). 34 patients were given of a sublingual NTG (0.6mg) 1 minute before the CT scan (NTG group), and the others were not (non-NTG group). The optimal reconstruction interval was chosen from different phase settings (range 30%-75% of RR interval). 2 radiologists assessed the significant stenosis (���50%) of coronary artery according to the modified 16 segments model of the American Heart Association. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy were calculated on a per-segment basis in comparison with the CAG as a gold standard. Results : Of 990 segments, 15 were excluded due to bad quality [severe calcification (n=5), artifact due to respiration (n=3), cardiac motion (n=3), adjacent contrast filled structure (n=2) and air in contrast (n=2)], and 975 were evaluated. There were 510 segments in NTG group and 465 in non-NTG group. There were no statistically significant differences in age, sex, heart rate, BP, and interval between CTCA and CAG (19.4짹18.8 days). The sensitivity, specificity, PPV, NPV, diagnostic accuracy in NTG group were 91.5%, 99.1%, 91.5%, 99.1% and 98.4% respectively, which were significantly higher than 74.2%, 96.3%, 59.0%, 98.1% and 94.8% of the non-NTG group (p<0.05). Conclusion : Using sublingual NTG improves diagnostic accuracy of ECG-gated 64-MDCT coronary angiography for the coronary artery stenosis, as compared with non-NTG group.