Little is known regarding the effects of coronary collateral circulation (CCC) on the prognosis of patients with chronic total occlusion (CTO) under different treatment strategies.We analyzed a total of 1124 patients who had been diagnosed with CTO and divided them into groups with good CCC (grade 2 to 3, n = 539) or poor CCC (grade 0 to 1, n = 531). The primary outcome was cardiac death during follow-up; the secondary outcome was major adverse cardiovascular events (MACEs). We also performed subgroup analyses in groups with and without CTO revascularization (CTO-R and CTO-NR, respectively), and sensitivity analyses excluding patients who received failed CTO-PCI, to further investigate the effect of CCC.During a median follow-up duration of 23 months, we did not detect any significant differences between the good CCC group and the poor CCC group in terms of cardiac death (4.2% vs 4.1%; adjusted hazard ratio [HR], 1.01; 95% confidence interval [CI], 0.56-1.83; p = 0.970) and MACEs (23.6% vs 23.2%; adjusted HR, 1.07; 95% CI, 0.84-1.37; p = 0.590). Subgroup analyses according to CTO revascularization showed similar results. In addition, we observed no differences in sensitivity analyses when patients who received failed CTO-PCI were excluded.Good CCC was not associated with a lower risk of cardiac death or MACEs among patients with CTO, regardless of whether the patients received CTO revascularization treatment.Copyright © 2022 Hellenic Society of Cardiology. Published by Elsevier B.V. All rights reserved.