Objectives. Frontal plane QRS-T angle is a novel marker of myocardial repolarization, and an increased frontal plane QRS-T angle is associated with adverse cardiac outcomes. Slow coronary flow may cause fatal cardiac arrhythmias by causing electrical abnormalities and altering ventricular repolarization. We aimed to evaluate the frontal plane QRS-T angle in patients with slow coronary flow. Design. A total of 60 consecutive patients with slow coronary flow and 60 consecutive patients with normal coronary flow were enrolled into the study. Laboratory and some electrocardiography parameters including frontal plane QRS-T angle were compared between the two groups. Results. We have found that the angle of frontal QRS-T was higher in the group with slow coronary flow (p < .001). In addition, there was a negative correlation between thrombolysis in myocardial infarction frame count and frontal QRS-T angle (r = -0.496, p < .001). Conclusions. In conclusion, increased frontal plane QRS-T angle might be an important indicator of slow coronary flow.