Diabetic patients have a higher restenosis rate and late morbidity following balloon angioplasty. However, the increased risk of restenosis after coronary stent implantation in diabetic patients is controversial. We compared the quantitative coronary angiographic (QCA) variables between 42 diabetic patients and 71 non-diabetic patients undergoing coronary stent implantation and for 6 months follow-up. Pre-procedural variables were identical in the diabetic and non-diabetic patients. The stent-artery ratio was lower (1.07+/-0.13 vs. 1.13+/-0.13, P=0.020), and acute gain after coronary stenting was lower (1.58+/-0.53 vs. 1.77+/-0.48, P=0.049) in the diabetic patients than in the non-diabetic patients. However, the late lumen loss (0.42+/-0.64 vs. 0.49+/-0.69), loss index (0.28+/-0.49 vs. 0.28+/-0.45), restenosis rate (19 vs. 23%) and target lesion revascularization rate (17 vs. 18%) after 6 months were identical in the diabetic and non-diabetic patients. These results suggest that diabetes itself does not increase stent restenosis.