Background and Aims: Pulse wave velocity (PWV), as a maker of arterial stiffness, is increased in coronary artery disease (CAD) and type 2 diabetes (DM) as an independent predictor of cardiovascular disease. The aim of this study was to evaluate the possibility of the improvement the arterial stiffness of DM with severe CAD after percutaneous coronary intervention (PCI). Methods and Results: The 102 patients with more than 70 % coronary stenosis were undergoing PCI. The 36 (35%) patients were DM and 66 (65%) were non-DM. Regional arterial stiffness was measured by noninvasive automatic device using tonometry method at serially (before and 3 months after PCI). Blood lipid-profile, adiponectin and hsCRP were measured.The level of central arterial (carotid-femoral;cf) PWV was higher in patients with smoker (p=0.0038), old age (p=0.0002), high systolic BP(p=0.0112), high mean BP (p=0.0195), high pulse pressure (p=0.0479). The level of leg (femoral-dorsalis p: fd) PWV was higher in female (p=0.0215), smoker (p=0.0337), high BMI (p=0.0058), high waist circumference (p=0.0122), and high blood creatinine level (p=0.0021). The level of cfPWV was much higher in DM group compared to non-DM group (9.23m/s짹1.48 vs. 8.21m/s짹1.07, p=0.0006). There was no differences in peripheral arterial (fd and carotid-radial;cr) PWV between DM group and non-DM group. The more number of diseased vessels affected the cfPWV velocity (1 or 2 VD vs. 3 VD:8.39 m/s짹1.25 vs. 9.17m/s짹1.47, p=0.0022). The difference of cfPWV level in DM group was much more improved than to the non-DM group which was performed before and 3 months after PCI (∆0.18m/s vs. ∆0.06m/s, p=0.0025). The difference of peripheral PWV before and 3 months after PCI also showed a tendency of improvement in both DM group (∆crPWV=∆0.32m/s, ∆fd-PWV=∆0.06m/s, p>0.05) and non-DM group (∆crPWV=∆0.25m/s, ∆fd-PWV=∆0.01m/s, p>0.05). The level of adiponectin in the treated DM group was higher than the non-DM group (1.084ug/ml짹0.855 vs. 0.737ug/ml짹0.767, p=0.0588). Conclusions: This study showed that intensive treatment could improve the central arterial stiffness of very high-risk group such as diabetic CAD.