Objective: In the treatment of coronary artery disease, stent implantation has become the standard treatment, but development of in-stent restenosis (ISR) limits the benefit of this treatment modality. Methods: Based on the connection between oxidative stress and thiol/disulphate and NRF2, it was intended to measure NRF2 and thiol/disulphate levels. Results: Coronary angiography images of 76 stable angina pectoris patients were evaluated. Of the 51 patients with a history drug eluting stent implantation, we determined 25 patients with ISR (Group 1) and 26 patients without ISR (Group 2). Twenty-five patients with normal coronary arteries were included in the study as control group (Group 3). NRF2 level was found to be significantly higher in patients who did not develop ISR (p=0.01). Total thiol was significantly higher in group 3 (738.76 micromole/L) compared to group 1 (626.11 micromole/L) and group 2 (630.27 micromole/L) (p=0.014). Native thiol was also significantly higher in group 3 (570.53 micromole/L) compared to group 1 (483.91 micromole/L) and group 2 (501 micromole/L) (p=0.006). Conclusion: We think that total and native thiol levels might be useful as an indicator of oxidative stress in early diagnosis of coronary artery disease, and the NRF2 level can be used in predicting patients who might develop coronary ISR.