Objective: We investigated the plasma levels and utility of miR-126, miR-208 and miR-146a in patients with cardiac syndrome- X (CSX). Patients and methods: The study included 54 patients (49.5 ± 9.9 years of age) with CSX (typical chest pain, positive exercise stress test, and normal coronary angiograms) and 32 age and sex matched control subjects. Endothelial function was assessed utilizing brachial flow mediated (FMD) and nitroglycerine flow mediated dilation (NMD). RNA was extracted and isolated from the sera and miRNA-126, miR-208 and miRNA-146a levels were detected by fluorescent quantitative polymerase chain reaction. Results: FMD was significantly decreased in patients with CSX compared to controls, associated with significant increase in hs-CRP, IL-6 and TNF-α. miR-126 expression was significantly decreased in CSX patients compared to controls (P<0.001), whilst miR-208 and 146a expressions were significantly increased (P<0.001). The dysregulation of the three miRNAs were significantly correlated with the degree of endothelial dysfunction (P<0.001 for all). Moreover CSX patients with impaired myocardial perfusion (IMP) had a significantly downregulation in miR-126 whilst both 208 and 146a were significantly upregulation (P<0.001) compared to those with normal myocardial perfusion. Of note miR-126, miR-208 and miR-146a have a good discrimination in predicting IMP in patients with CSX. Conclusion: The current study indicated that serum miR-126, miR- 208 and miR-146a are significantly deregulated and correlated with endothelial dysfunction in CSX patients. They were independent markers of myocardial perfusion in CSX patients and might be of great predictive value in risk stratification of patients with syndrome-X.