Aim. To elucidate sonographic characteristics of common carotid arteries in adolescents with type1 diabetes mellitus (DM1) depending on the duration of the disease and thepresence of chronic complications. Materials and methods. A total of 56 adolescents having DM1 of different duration were examined to evaluate conditions of common carotid arteries (CA) in the systole anddiastole during at least 3 cardiac cycles. The following parameters were measured: CA diameter, intima-media thickness (IMT), estimated stretch and stiffness coefficients, Youngsmodulus. The control group comprised 16 healthy adolescents. Results. Bilateral increase of IMT was recorded in patients with DM duration over 5 years. Youngs modulus, stretch and stiffness coefficients were virtually unrelated to diseaseduration. In patients having DM for more than 10 years, stretch coefficient was 5.38 (95% DI 4.82-5.8) compared with 5.82 (95% DI 5.63-7.38) in those with DM for less than 3years (p = 0.04). The level of albuminuria correlated with IMT (r=0.32, p=0.03), stiffness coefficient (r = 0.43, p=0.001), stretch coefficient (r= -0.48, p