Background Sirolimus-eluting stents (SES) are reported to be associated with reduced late lumen loss (LLL),resulting in less frequent restenosis when compared to bare-metal stent.The current study aimed to assess the difference in LLL between SES with biodegradable and with permanent polymer.Methods From March 2010 to June 2011,300 consecutive patients having only biodegradable polymers or permanent polymer SES for all diseased vessels were included.Serial quantitative coronary analysis was performed on both the in-stent and segment area,including the stented segment,as well as both five mm margins proximal and distal to the stent.The primary endpoint was the LLL defined as the minimal lumen diameter (MLD) post-stenting minus the MLD at nine-month after the indexed procedure.Results LLL was comparable between the two stents.Importantly,LLL for the distal segment (median 0.05 mm,interquartile 0 to 0.09 mm) was less severe compared with i n-stent (median 0.13 mm,interquartile 0.08 to 0.18 mm) and proximal segment LLL (median 0.12 mm,interquartile 0.06 to 0.14 mm,all P＜0.001).In general,the LLL was associated with the post-procedure MLD (b=0.28,P=0.002),hyperlipidemia (b=0.14,P=0.021),and calcified lesions (b=0.58,P=0.001).The R2 and Radj of the multiple regression model were 0.651 and 0.625,respectively.Conclusions SES with either biodegradable or permanent polymer had lower value of LLL.The small amount of LLL at the distal seoment oossiblv contributed to the less distal edge stenosis.