Aim. To study the nature and severity of heart rate variability (HRV) and heart rate turbulence (HRT) abnormalities in patients with coronary artery disease (CAD) and type 2 diabetes mellitus (T2DM) and to assess the prevalence of cardiovascular autonomic neuropathy (CAN) and its severity in patients with T2DM concurrent with CAD. Subjects and methods. A total of 185 patients with T2DM and/or CAD were examined and divided into 3 groups: 1) 92 patients with CAD and T2DM; 2) 43 patients with CAD without T2DM; 3) 49 patients with T2DM without CAD. All the patients underwent 24-hour ECG monitoring with HRV and HRT analysis. Results. CAN was identified and the severity of CAN was assessed based on the abnormal HRV and HRT parameters. CAN, especially severe one, was more common in Group 1 (the relative risk was 3.3 [95% CI 1.3—8.2]; p<0.05), than in Group 3. In Group 1, CAN was associated with the duration of T2DM and the level of glycated hemoglobin (p<0.05). The patients with severe CAN in Group 1 showed a 4-fold higher risk for multivessel coronary artery lesions than those without CAN (p<0.05). Conclusion. Glycemic control quality, T2DM duration, and obvious coronary atherosclerotic lesions were demonstrated to be associated with the presence and severity of CAN. The developed methods may be used in practice to detect and more accurately determine the severity of CAN and to predict cardiovascular risk in patients with T2DM and CAD.