Because it is a nidus for thrombus formation, LSM may contribute to late thrombosis. However, the background frequency and predictors of LSM after BMS implantation are not sufficiently evaluated. We evaluated the incidence and predictors of LSM after BMS implantation in 876 patients with 994 native lesions who performed intravascular ultrasound study at index and after 6 months of follow-up. LSM was defined as a separation of stent struts from the intimal surface of the arterial wall and evidence of blood flow behind the strut that was not presented at post-implantation. LSM occurred in 53 lesions (5.3%). The maximum area of LSM measured 2.9짹2.3 mm2. There was an increase of EEM area (19.0짹4.0 to 23.3짹5.6, p<0.001) and plaque area (9.7짹3.0 to 11.1짹3.4, p<0.001). The increase in EEM was greater than the increase in plaque. LSM area correlated with directly with the increase in EEM area (r=0.702, p<0.001). The incidence of LSM in elective stenting after balloon dilation was 4.2%. The predictors of LSM were primary stenting for acute myocardial infarction (11.5% vs. 4.2%, p=0.006) and directional coronary atherectomy before stenting (10.2% vs. 4.2%, p=0.02). Conclusion: LSM occurs in about 4-5% after BMS implantation. Deep vessel injury (e.g. aggressive directional coronary atherectomy) during stenting procedure or underlying thrombus resolution during follow-up might be associated with the development of LSM.