Background: there is a strong relationship between epicardial fat thickness and severity of coronary artery disease. The impact of diabetes on severity of coronary artery disease (CAD) is well known. The possible impact of diabetes on the relationship between EFT and severity of CAD was not fully investigated. Patients and Methods: The study included 52 patients with NSTEMI (mean age: 54.3±6.7years). Patients were classified into two groups according to presence of diabetes (diabetic group (24 patients) and non-diabetic group (28 patients)). EFT was measured by transthoracic echocardiography on the right ventricle in individuals having the left lateral decubitus position GENSINI score was used to define the severity of CAD. Results: Diabetic patients had higher EFT values compared with non-diabetics (p < 0.05). EFT is independently associated with diabetes and GENSINI score in all patients (p < 0.05, for all). When patients were divided into two groups, as diabetic and non-diabetic, the association between EFT and GENSINI score was stronger in diabetic patients compared with non-diabetics (r = 0.6618; p< 0.001vs. r = 0.330; p = 0.04). Conclusion: Epicardial fat thickness is associated with GENSINI score in both diabetic and non-diabetic patients suffering from NSTEMI. Furthermore, there is a stricter relationship between EFT and GENSINI score in diabetic patients