Optical coherence tomography (OCT), a new imaging modality, has shown a superior ability in detecting and distinguishing different types of plaques (fibrous, fibrocalcific, and lipid-rich plaques), in visualizing of vascular microstructures such as intraluminal thrombi, vascular dissection, and structure of restenotic tissues, and finally in identifying vulnerable plaques, otherwise missed by intravascular ultrasound. However, limitations in the use of OCT such as poor penetration and its attenuation by blood or the clinical relevance of OCT should be clarified through further investigation, and careful attention should be paid to the future studies on OCT.