Background: Coronary angiography (CAG) is the gold standard in the diagnosis and treatment of the coronary artery disease, but has several limitations. Intravascular ultrasound (IVUS) and fractional flow reserve (FFR) have been widely used to assess anatomic and physiologic severity and to determine the necessity of revascularization. In recent years, multidetector coronary computed tomographic angiography (CCTA) has become popular. The aims of this study were to evaluate the correlation among IVUS, CCTA, and FFR in intermediate coronary stenosis and to assess the diagnostic accuracy of CCTA and IVUS parameters for defining the presence of myocardial ischemia. Methods: 123 patients with intermediate stenosis were prospectively enrolled from 4 centers. IVUS and FFR examination were performed simultaneously for all segments. All patients underwent CCTA before the invasive angiography. Functionally significant stenosis was defined as FFR less than 0.80. All angiographic, CCTA and IVUS data were analyzied in core laboratories. Results: 159 coronary artery segments in non-distal and dominant vessels were analyzed. The mean IVUS minimal lumen area (MLA) was 3.67 짹 1.68 mm짼(mean 짹 SD), mean FFR was 0.85 짹 0.10 (mean 짹 SD), and mean CCTA percent diameter stenosis (%DS) was 49.96 짹 13.68 % (mean 짹 SD). IVUS MLA and FFR had significant correlation (r = 0.606, p <0.001). CCTA %DS had significant negative correlation with FFR(r = –0.564, p <0.001). Minimum lumen diameter by CCTA and FFR had moderate correlationn (r = 0.551, p < 0.001). Best cutoff values (BCV) to predict the functionally significant stenosis were IVUS MLA <3.0mm짼 (sensitivity of 92.3% and specificity of 72.7%) and <2.7mm짼 (sensitivity of 79.5% and specificity of 81.9%) by area under curve (AUC) 0.92 BCV of CCTA were CCTA %DS >50% (sensitivity of 92.3% and specificity of 61.4%) and CCTA %DS >55% (sensitivity of 74.4% and specificity of 77.7%) by AUC 0.87. In the multivariate analysis, MLA by IVUS (p<0.001), and %DS of CCTA (p<0.001) were the predictor of the functionally severe stenosis Conclusion: MLA by IVUS and %DS in CCTA had a correlation with FFR. Anatomical cutoff values from IVUS and CCTA can predict the functionally significant stenosis in selected patients with intermediate stenosis.