Objective. To analyze the effect of long-chain (LC) polyunsaturated w-3 fatty acids (PUFAs) on the daily arterial stiffness parameters in patients with type 2 diabetes (DM2) and cardiovascular autonomic neuropathy (CAN). Material and methods. The study involved 39 patients with DM2 and verified functional stage of CAN. Patients were divided into 2 groups: therapy group (n=21) and control group (n=18). Patients of the control group received traditional hypoglycemic therapy; patients of the therapy group additionally received 1 capsule/day of the ω-3 PUFAs for three months. Results. The use of the ω-3 PUFAs resulted in a statistically significant decrease in aortic augmentation index (AAI) and pulse wave velocity in the aorta (PWV) during the active period. There was a decrease in AAI in the aorta and the brachial artery and in PWV in the aorta during the night. Conclusion. The efficacy of ω-3-PUFAs is a result of a direct effect of the pharmacological agent on the circadian arterial stiffness parameters.