Recent advances in intra-coronary imaging modalities have enabled us to evaluate precise plaque morphologies and vascular response to coronary stents in vivo. Superior resolution of optical coherence tomography (OCT) allows the measurement of fibrous cap thickness and detection of macrophage accumulation, both of which are critical to identify vulnerable plaques. Poor penetration of OCT however limits the assessment of plaque volume and vessel remodeling, while intravascular ultrasound (IVUS) is capable of evaluating these parameters. Caution must be exercised when interpreting IVUS-based tissue characterization because this technology lacks sufficient resolution to evaluate plaque composition. In stented arteries, OCT has the ability to detect uncovered struts and abnormal neointimal tissues including fibrin deposition, inflammation (hypersensitivity), and neoatherosclerosis, especially following drug-eluting stent placement. These findings suggest a potential clinical benefit of OCT to assess the risk of future adverse cardiac events; at the same time understanding the limitation of this technology is also important.