<b>Aim: </b>Acute pancreatitis (AP) is a disease with inflammation, and patients present with severe acute upper abdominal pain in emergency departments. AP can result in higher mortality as its clinical severity increases. Therefore, in this study, we want to investigate the clinical utility of the systemic inflammation response index (SIRI) and systemic immune-inflammation index (SII) in showing the severity of AP.<br /> <b>Material and methods:</b> Among the patients admitted to our emergency department between January 2020 and December 2022, 201 patients diagnosed with AP were included in the study. These patients were divided into two groups according to the severity of the disease as mild and severe AP (MAP and SAP). Demographic data and laboratory data of the patients (white blood cell count, such as SIRI, SII and C-reactive protein, SIRI, SII and C-reactive protein) were recorded. Differences between groups of AP patients divided according to disease severity were analyzed.<br /> <b>Results: </b>165 (82.1%) patients had MAP and 36 (17.9%) patients had SAP. 52.8% of the patients were male. The mean of the SAP group was significantly higher than the SII MAP group (3165.71±3058.42 vs.1043.31±849.15; p&lt;0.001). In addition, SII levels were significantly higher in the SAP group compared to MAP (11.19±6.27 vs. 3.12±3.01; p&lt;0.001). In regression analysis, CRP, SIRI and SII was found to be able to predict SAP in patients with AP. &nbsp;The power of SIRI and SII were found to be higher in predicting SAP [AUC for SIRI: 0.890; [AUC for SII: 0.859].<br /> <b>Conclusion: </b>High SII and SIRI are useful markers that can show the severity of AP.<br /> <b>Key words: </b>acute pancreatitis severity, SII, SIRI, biomarker

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