<p><b>OBJECTIVE</b>To investigate the impact of statin use on coronary flow reserve (CFR) in patients with slow coronary flow.</p><p><b>METHODS</b>A total of 91 patients with chest pain and coronary slow flow but normal coronary angiography were included in this study, patients were divided into statin group (atorvastatin 20 mg/d for 8 weeks, n = 51) and non-statin group (n = 40), 26 healthy subjects with normal angiography and negative exercise ECG test served as normal controls. Blood cholesterol was measured. Doppler coronary flow velocity and Doppler reserve measurement of distal left anterior descending were recorded at rest and adenosine infusion (140 microgxkg(-1)xmin(-1)) induced hyperemia state, CFR was calculated by the ratio of maximal hyperemia and baseline peak diastolic coronary flow velocity (hCFV and bCFV) before and after atorvastatin treatment.</p><p><b>RESULTS</b>(1) Eight weeks later, total cholesterol and LDL-C levels were significantly lower in statin group than in non-statin group and control group [TC (3.83 +/- 0.80) mmol/L vs. (5.30 +/- 1.18) mmol/L vs. (5.32 +/- 1.17) mmol/L, P < 0.05; LDL-C (2.26 +/- 0.64) mmol/L vs. (3.28 +/- 0.85) mmol/L vs. (3.30 +/- 0.82) mmol/L, P < 0.05]. (2)Baseline CFR levels were significantly lower in statin group and non-statin group than that in control group (2.32 +/- 0.30 vs. 2.25 +/- 0.33 vs. 3.15 +/- 0.34, P < 0.05). Compared with non-statin group and statin group before treatment, 8 weeks statin treatment was associated with reduced bCFV [(26.06 +/- 3.22) cm/s vs. (29.02 +/- 3.36) cm/s and (26.06 +/- 3.22) cm/s vs. (28.43 +/- 3.40) cm/s, P < 0.05], increased hCFV [(77.63 +/- 8.96) cm/s vs. (65.17 +/- 7.22) cm/s and (77.63 +/- 8.96) cm/s vs. (64.58 +/- 6.26) cm/s, P < 0.05] and increased CFR (3.07 +/- 0.29 vs. 2.28 +/- 0.35 and 3.07 +/- 0.29 vs. 2.32 +/- 0.30, P < 0.05). bCFV, hCFV and CFR of statin group post treatment were similar to those of controls (P > 0.05).</p><p><b>CONCLUSION</b>Patients with coronary slow flow were associated with lower CFR which could be significantly improved by statin therapy.</p>