Objective: To investigate the association of IR with metabolic and vascular disorders related to diabetes, we analyzed 7,109 Korean type 2 diabetic patients according to IR. Methods: A total 7,109 patients with type 2 diabetes were recruited through Huh’s Diabetes Center from January 2003 to June 2009. Insulin sensitivity was measured by a rate constant for plasma glucose disappearance (Kitt, %/min) using short insulin tolerance test. Subgroup analyses were performed according to the tertiles of Kitt. Results: Mean age was 58.1 ± 10.1 years old, and 71.5% of diabetic patients had IR. Patients with the lowest tertile of Kitt (IR group) showed higher levels of metabolic parameters such as body mass index (BMI), visceral fat thickness, blood pressure, fasting blood glucose, HbA1c, total cholesterol, triglyceride and LDL cholesterol but lower HDL cholesterol compared to the patients with the highest tertile of Kitt (insulin-sensitive group). Mean and maximal IMT of carotid arteries was significantly higher in the patients with the lowest tertile of Kitt. As the value of Kitt was lower, the prevalence of metabolic and vascular disorders related to diabetes increased. In multiple regression analysis, IR was an independent risk factor for the metabolic and vascular disorders related to diabetes after adjusting for age, sex, duration of diabetes, BMI and HbA1c. Odds ratios for metabolic syndrome and carotid atherosclerosis in patients with the lowest tertile of Kitt were 3.108 (95% CI, 2.721~3.549) and 1.232 (95% CI, 1.069~1.418), respectively. Conclusion: IR is not only prevalent but also an important predictor for metabolic and vascular disorders in Korean patients with type 2 diabetes. Beyond reducing the HbA1c, management focusing on IR such as life-style modification or using insulin-sensitizing agents should be evidently needed in patients with type 2 diabetes.