Objectives: Bypassing a patently stented coronary artery has a risk of flow competition, and leaving it ungrafted has a high risk of stent restenosis. This study determines the fate of patently stented coronary arteries bypassed and left ungrafted. Materials and Methods: Patients undergoing isolated coronary artery bypass grafting (CABG) with previous percutaneous coronary intervention (PCI) were retrospectively scanned between January 1, 2015, and January 1, 2020. Patients undergoing surgery with a patently stented coronary artery were identified. Postoperative coronary angiography was performed in 52 of these patients. Results: There were 24 patients whose patently stented coronary artery was bypassed and 28 whose patently stented coronary artery was not bypassed. The median follow-up time was 49 months in the non-bypass group and 53.5 months in the bypass group. Twenty (71.4%) patently stented coronary arteries remained open in the non-bypass group, and 23 (95.8%) vessels were open in the bypass group (p=0.02). The estimated open rate of vessels was 56% in the non-bypass group and 95% in the bypass group at five years (log-rank p=0.01). Major adverse cardiac events were developed in 12 (42.8%) patients in the non-bypass group and 6 (25%) patients in the bypass group. Conclusion: Patients with an open stented vessel that was not bypassed during CABG have a risk of in-stent restenosis and major adverse cardiac events during the mid-and long-term periods. It may not be safe to leave patently stented coronary arteries ungrafted, particularly those with bare metal stents.