Background Despite the high resolution of optical coherence tomography (OCT) imaging, the accurate assessment of the coronary plaque composition is limited. Methods Pre-intervention OCT and virtual histology intravascular ultrasound (VH-IVUS) was performed in the culprit lesions. Fibrous cap thickness was measured at its thinnest part. Thin-cap fibroatheroma (TCFA) was defined as lipid rich plaque (��� 2 quadrants) with a fibrous cap thickness < 65關m. VH-IVUS analysis was performed at the site of the largest necrotic core. Results 41 coronary lesions were analyzed and OCT-derived TCFA was found in 23 plaques (56%). Plaque classified as TCFA had a larger P&M area than non-TCFA plaques (p=0.024). In VH-analysis, TCFA showed significantly larger necrotic absolute area as compared to non-TCFA without the difference of fibrous, fibrofatty and dense calcium components (Table). Conclusions TCFA identified by OCT imaging showed more unstable tissue compositions with larger plaque and necrotic core area compared to non-TCFA.