Background The aim of this study was to investigate Paraoxanase 1 (PON-1) activity in patients with ST-elevated and non-ST-elevated acute myocardial infarction (AMI) and to determine its correlation with Gensini scores (GSs). Methods A total of 109 patients with AMI and 58 healthy subjects as control group were included in the study. Patients were divided into 2 subgroups as ST-elevated and non-ST-elevated AMI patients (Group I and II, respectively). Controls were named as Group III. PON-1 activity was determined on admission to emergency department for each group. In addition, GSs for patient groups were determined. Then, groups were compared according to their results. Results PON-1 levels in Group I and II were significantly lower when compared to Group III. Median GSs for Group I and II were 60 and 64, respectively. The cut-off value of PON-1 for diagnosis of AMI was ≤ 180 U/L, which was identified by receiver characteristics receiver curve analysis. However, we could not determine a significant relationship between serum PON-1 levels and GSs in patients with AMI. Conclusion PON-1 levels measured on admission to emergency department may be used to rule out AMI. PON-1 levels in AMI patients are found to be inefficient in determining extension of ischemia measured by GS.