Aims The Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial (REDUCE-IT) trial demonstrated that icosapent ethyl lowered the risk of atherosclerotic cardiovascular disease (ASCVD) among patients with elevated triglycerides. However, how to appropriately implement its use in clinical practice is not well-defined. We aimed to determine whether plaque burden as assessed by coronary artery calcium (CAC) could stratify ASCVD risk among patients eligible for icosapent ethyl. Methods and results Among 23 759 patients who underwent computed tomography angiography (CTA) in the Western Denmark Heart Registry, we identified eligibility for the REDUCE-IT trial. A total of 2146 participants (9%) met enrolment criteria for REDUCE-IT. During a median of 4.3 years of follow-up, 146 ASCVD events occurred. Overall, there was a stepwise increase in ASCVD event rates per 1000 person-years with increasing CAC (CAC = 0: 10.5, CAC 1-299: 18.7, CAC >= 300: 49.8). REDUCE-IT-eligible patients with CAC >= 300 had a multivariable-adjusted hazard ratio of 3.1 compared with CAC = 0 (95% confidence interval: 1.9-4.9). Coronary artery calcium differentiated risk similarly in patients with and without obstructive coronary artery disease (CAD). Overall, the 5-year estimated number needed to treat to prevent one event with icosapent ethyl was 45 and ranged from 87 in those with CAC = 0 to 17 in those with CAC >= 300. Some patients with non-obstructive CAD had lower estimated number needed to treat than patients with obstructive CAD when their plaque burden was higher. Conclusion Atherosclerotic plaque burden as assessed by CAC can identify REDUCE-IT-eligible patients who are expected to derive most, and least, absolute benefit from treatment with icosapent ethyl regardless of obstructive versus non-obstructive CAD status.