It is now generally recognized that acute coronary syndromes most commonly result from disruption of thin-cap fibroatheroma (TCFA), which is characterized by a large necrotic core with an overlying thin-fibrous cap measuring <65μm. Recent advances in intracoronary imaging modalities have significantly improved the ability to detect TCFA in vivo. Intravascular ultrasound (IVUS) is perhaps the most promising modality that has been used more than 15 years to evaluate atherosclerotic plaque. IVUS has revealed a lot of the clinical evidence regarding vulnerable plaque detection in live humans. Recently, by analyzing the IVUS acoustic signal before demodulation and scan conversion, IVUS radiofrequency analysis can be used to differentiate adjacent smaller areas of atherosclerotic plaque with heterogeneous composition. Coronary angioscopy allows direct visualization of the coronary artery wall and provides detailed information of the luminal surface of plaque, such as color, thrombus or disruption. Optical coherence tomography imaging, recently been introduced for in vivo human imaging, offers a higher resolution than any other available imaging modality, and can visualize a thin fibrous cap measuring <65μm. In this review, we will discuss the features and limitations of each imaging modalities for detecting TCFA.  (Circ J 2013; 77: 588–595)