Abstract: AIM To explore the clinical significance and correlation between serum leptin levels, insulin resistance, and coronary slow flow. METHODS 110 patients with coronary stenosis <50% according to coronary angiography (CAG) were included. They were divided into two groups: CSFP group (n=48) and NCF group (n=62). Coronary artery TIMI frame count of the left anterior descending branch (LAD), the left circumflex branch (LCX), and right coronary artery (RCA) in the CSFP group and NCF group were recorded. The level of fasting serum leptin was examined by enzyme linked immunosorbent assay (ELISA). The insulin resistance index (HOMA-IR) was calculated according to HOMA model (HOMA-IR=FBG×FINS/22.5). The correlation between serum leptin levels, insulin resistance, and coronary slow flow was analyzed. The diagnostic value of serum leptin and HOMA-IR on CSFP was evaluated by receiver operating characteristic (ROC) curve. RESULTS Single factor analysis demonstrated that leptin levels, HOMA-IR, age, gender, smoking and blood lipids, and 4 other indicators were related to CSF. Multivariate analysis revealed that only leptin and HOMA-IR were independent factors associated with CSF. Serum leptin levels were positively correlated with mean TFC (r=0.816, P<0.01); HOMA-IR was positively correlated with mean TFC (r=0.622, P<0.01). Serum leptin levels weree positively correlated with HOMA-IR (r=0.484, P<0.01). The serum leptin level and HOMA-IR ROC curves of CSF patients were analyzed. The results showed that the area under the diagnostic curve of leptin and IR to CSF was statistically significant (P<0.01) and the area under the curve was 0.972, 0.836. CONCLUSION Serum leptin levels and insulin resistance are associated with CSFP, which have certain diagnostic value for CSF.