Successful revascularization for chronic total occlusion (CTO) lesions was known to be associated with better long-term survival, including improved left ventricular (LV) function, symptom relief, and quality of life . However, percutaneous coronary intervention (PCI) of CTO lesions remains one of the most challenging procedural subsets because it has a higher rate of procedural failure (20% to 35%) and higher complication rate than non-CTO procedure . The overall success rate from the nationwide Korean multicenter CTO registry (K-CTO registry) was 81.6% (2632/3271 patients enrolled in 2007) . In real-world clinical practice, the prevalence of diabetes mellitus (DM) has been shown to be 10% to 35% of all CTO patients . In the K-CTO registry, the prevalence of DM was 34.8% (1139/3271 patients) and in Korea University Guro Hospital, a dedicated high-volume CTO PCI center in Korea, the prevalence of DM was 44% (363/822) from a previous report . In general, these DM patients have a higher risk of cardiovascular events and death than those without DM ; furthermore, stenting for coronary artery lesions in DM patients is known to be associated with significantly higher in-stent restenosis (ISR) rates of 32% to 66% and remains a challenging clinical problem . These proven worse clinical outcomes might be similarly translated and implicated into DM CTO patients even following successful CTO PCI with current-generation drug-eluting stents (DES). However, due to the nature of study characteristics, this topic will be very difficult to conduct a good randomized clinical trial with a larger study population for which to make a definitive conclusion. Even though there is a paucity of retrospective data comparing DM and non-DM CTO PCI patients treated with current-generation DES, cutting-edge professional and experienced CTO skills, dedicated and specialized devices, good surgical backup, and current-generation optimal medical therapy, including newly developed drugs for chronic heart failure and DM, which can positively impact prognosis, systemic review and meta-analysis is a practical way to get a good clinical message on this topic.