OBJECTIVES:To determine the diagnostic performance of CT coronary angiography (CTCA) in detecting and excluding left main (LM) and/or three-vessel CAD ("high-risk" CAD) in symptomatic patients and to compare its discriminatory value with the Duke risk score and calcium score. MATERIALS AND METHODS:Between 2004 and 2011, a total of 1,159 symptomatic patients (61 ± 11 years, 31 % women) with stable angina, without prior revascularisation underwent both invasive coronary angiography (ICA) and CTCA. All patients gave written informed consent for the additional CTCA. High-risk CAD was defined as LM and/or three-vessel obstructive CAD (≥50 % diameter stenosis). RESULTS:A total of 197 (17 %) patients had high-risk CAD as determined by ICA. The sensitivity, specificity, positive predictive value, negative predictive value, positive and negative likelihood ratios of CTCA were 95 % (95 % CI 91-97 %), 83 % (80-85 %), 53 % (48-58 %), 99 % (98-99 %), 5.47 and 0.06, respectively. CTCA provided incremental value (AUC 0.90, P < 0.001) in the discrimination of high-risk CAD compared with the Duke risk score and calcium score. CONCLUSIONS:CTCA accurately excludes high-risk CAD in symptomatic patients. The detection of high-risk CAD is suboptimal owing to the high percentage (47 %) of overestimation of high-risk CAD. CTCA provides incremental value in the discrimination of high-risk CAD compared with the Duke risk score and calcium score. KEY POINTS:• Computed tomography coronary angiography (CTCA) accurately excludes high-risk coronary artery disease. • CTCA overestimates high-risk coronary artery disease in 47 %. • CTCA discriminates high-risk CAD better than clinical evaluation and coronary calcification.