Abstract: AIM：To investigate the relationship between elevated plasma C-reactive protein (CRP) levels and coronary heart disease (CHD) in patients with type II diabetes mellitus (T2DM). METHODS: Sixty-one patients with CHD diagnosed by coronary angiography were divided into two groups: 30 cases with T2DM in group A and 31 cases without T2DM in group B, and 30 healthy subjects were assigned to group C as control. The levels of plasma CRP, fasting blood glucose (FBG), blood lipids and BMI were detected and compared between groups. RESULTS: Significant differences were found in the levels of CRP, FBG and HbA1c among the three groups. Gensini score and percentage of three-branch lesions in patients with T2DM were higher than those in patients without T2DM (P<0.01). Simple correlation analysis indicated that severity of coronary artery disease (CAD) was significantly correlated with CRP, TG, TC, HDL-C, LDL-C and body mass index (P<0.01). CONCLUSION: The coronary lesions of CHD patients with T2DM tend to be more widespread and more severe. Increased serum CRP level is an important risk factor for T2DM complicated with CAD and a vital parameter for diffuse CAD in patients with T2DM.