['Morphological characteristics of non-significant coronary plaques (NSCPs) that develop rapid progression have not been fully elucidated. The aim of this study was to clarify the morphological characteristics of NSCPs in patients with coronary artery disease (CAD) using intravascular optical coherence tomography (OCT).', 'Fifty-three consecutive CAD patients undergoing percutaneous coronary intervention were enrolled and 69 NSCPs (per cent diameter stenosis <50%) were identified on baseline angiogram. Baseline characteristics of NSCPs were evaluated by OCT, and patients were followed-up prospectively. At the second coronary angiography, the baseline OCT characteristics and plaque progression were correlated. During the 7-month follow-up period, 13 NSCPs showed angiographic progression and 56 NSCPs did not. Baseline minimum lumen diameter and diametric stenosis were similar between NSCPs with and without progression. Compared with NSCPs without progression, those with progression showed a significantly higher incidence of intimal laceration (61.5 vs. 8.9%, P < 0.01), microchannel (76.9 vs. 14.3%, P < 0.01), lipid pools (100 vs. 60.7%, P = 0.02), thin-cap fibroatheroma (TCFA) (76.9 vs. 14.3%, P < 0.01), macrophage images (61.5 vs. 14.3%, P < 0.01), and intraluminal thrombi (30.8 vs. 1.8%, P < 0.01). Univariate regression analysis showed that TCFA and microchannel images showed high correlation with subsequent luminal progression [odds ratio (OR): 20.0, P < 0.01 and OR: 20.0, P < 0.01, respectively].'] Do thin-cap fibroatheroma and microchannel findings in optical coherence tomography correlate with subsequent progression of coronary atheromatous plaques?