Diabetes (DM) is common in haemodialysis (HD) patients and affects both blood pressure (BP) and arterial stiffness. Carotid femoral pulse wave velocity (PWV) reflects the stiffness of the aorta and is regarded as a strong risk factor for cardiovascular (CV) mortality in HD patients. However, PWV is highly influenced by the BP-level. Higher PWV-values among HD patients with DM could reflect a higher BP-level rather than increased arterial stiffness. The aim of this study was to investigate the effect of DM on BP and PWV in a group of HD patients. BP and PWV were measured in 66 HD patients without DM (HD) and 32 HD patients with DM (HD+DM). The SphygmoCor system was used for estimation of PWV. HD-duration, age, gender and BP medication were similar in the two groups. Mean DM-duration was 23±11 years and 25(78%) had type 2 DM. HD+DM had higher BMI (26±5 vs. 29±5 kg/m2, p=0.02), systolic BP (142±20 vs. 152±21 mmHg, p=0.02) and pulse pressure (65±17 vs. 80±18 mmHg, p<0.001). There was no difference in diastolic BP, mean BP and heart rate. Mean PWV was 9.1±2.5 in HD and 12.3±3.1 m/s in HD+DM. The mean PWV difference HD vs. HD+DM was 3.1(1.9-4.3)m/s, p<0.0001 in unadjusted analysis. After adjustment for systolic BP, heart rate, and age the mean PWV difference remained significant (2.8(1.8-3.7)m/s, p<0.001). Adjustment with mean BP gave similar results. HD patients with DM have more progressed aortic stiffness than HD patients without DM for the same BP. This may explain why HD patients with DM are more prone to die from CV causes compared to HD patients without DM.