BACKGROUND: Abdominal pain is a common and non-specific symptom in children. It is important to be able to distinguish the source of abdominal pain before surgery. OBJECTIVES: Assess importance of the systemic immune inflammation index (SII), systemic inflammation response index (SIRI), and other systemic inflammatory response blood cell indices in predicting the diagnosis and prognosis of acute appendicitis in children. DESIGN: Retrospective cohort SETTING: Single center in Turkey PATIENTS AND METHODS: The files of patients with abdominal pain aged 0-18 years who underwent surgery for appendicitis in our clinic between January 2011 and January 2022 were reviewed. According to the pathology results, patients were divided into two groups, those with pathologic findings of appendicitis (positive for appendicitis) and those without appendicitis. Systemic inflammation markers were statistically compared between the groups. MAIN OUTCOME MEASURES: Systemic inflammation markers. SAMPLE SIZE: 1265 patients RESULTS: Of the 1265 patients, 784 (62%) were male and 481 were female (38%). According to the pathologic examinations, 256 (20.2%) patients did not have appendicitis, and 1009 (79.8%) patients had acute appendicitis. The SIRI level was significantly higher in patients with acute appendicitis compared with patients without acute appendicitis (P<.001). Levels of SII were significantly higher in patients with acute appendicitis (P<.001). CONCLUSION: In children presenting with abdominal pain, high SIRI and SII values alone support the diagnosis of acute appendicitis at a rate of 95%. When physical examination findings, duration of pain, and imaging test results are added, the diagnosis becomes clear at a rate of 98%. LIMITATIONS: Single-center study and retrospective.