Certain coronary anomalies are associated with high risk features. We sought to determine the diagnostic accuracy of coronary computed tomographic angiography (CTA) in determining high-risk features, particularly intramural segments. Anomalous coronary arteries can be associated with adverse clinical events. Anomalous coronaries that course between the great vessels (interarterial) have been associated with sudden death. High-risk features of interarterial vessels described in the literature include; a slit-like orifice, acute angle of origin, and intramural segments (within the wall of the aorta). Although computed tomography (CT) findings of acute angle and slit like orifice have been described previously no prior evaluations regarding CT identification of an intramural segment have been reported. An intramural segment has distinct surgical management implications. All interarterial anomalous coronary arteries do not have an intramural segment. Since October 2004, 15 patients were diagnosed by CTA as having an anomalous coronary artery with an interarterial course, which were then confirmed by intraoperative examination of their coronary origins and course during aortic root/coronary artery surgery. The CTA images were retrospectively analyzed for the presence of high-risk features by a radiologist blinded to the surgical findings. Comparison of these findings was made to the findings at surgery. The anomalous coronary was the right coronary artery in 10 patients and the left coronary artery in 5. Eleven patients had an intramural segment identified at surgery. Pre-operative coronary CTA showed that all patients with an intramural course of the anomalous artery, had slit-like orifice, an acute angle of origin (mean 18.4 ± 3.4°), and an elliptical shaped cross-section throughout the intramural segment of the anomalous vessel. The average vessel height/width ratio for anomalous coronary vessels without an intramural segment was 1.03; compared to a ratio of 2.19 for anomalous vessels with an intramural segment (P = 0.003). Coronary CTA can identify an intramural segment of an anomalous interarterial coronary artery by its elliptical shape. Identifying an intramural segment has important clinical and surgical implications.