Aims To evaluate the feasibility of the combined use of virtual histology (VH)-intravascular ultrasound (IVUS) and optical coherence tomography (OCT) for detecting in vivo thin-cap fibroatheroma (TCFA). Methods and results In 56 patients with angina, 126 plaques identified by IVUS findings were analysed using both VH-IVUS and OCT. IVUS-derived TCFA was defined as an abundant necrotic core (> 10% of the cross-sectional area) in contact with the lumen (NCCL) and %plaque-volume > 40%. OCT-derived TCFA was defined as a fibrous cap thickness of < 65 mu m overlying a low-intensity area with an unclear border. Plaque meeting both TCFA criteria was defined as definite-TCFA. Sixty-one plaques were diagnosed as IVUS-derived TCFA and 36 plaques as OCT-derived TCFA. Twenty-eight plaques were diagnosed as definite-TCFA; the remaining 33 IVUS-derived TCFA had a non-thin-cap and eight OCT-derived TCFA had a non-NCCL (in discord with NCCL visualized by VH-IVUS, mainly due to misreading caused by dense calcium). Based on IVUS findings, definite-TCFA showed a larger plaque and vessel volume, %plaque-volume, higher vessel remodelling index, and greater angle occupied by the NCCL in the lumen circumference than non-thin-cap IVUS-derived TCFA. Conclusion Neither modality alone is sufficient for detecting TCFA. The combined use of OCT and VH-IVUS might be a feasible approach for evaluating TCFA.