Background. This study aimed to evaluate Pediatric Appendicitis Score (PAS), diagnostic delay, and factors responsible for possible late diagnosis in children <4 years compared with older children who were operated on for suspected appendicitis.Method. 122 children, between 1 and 14 years, operated on with appendectomy for suspected appendicitis, were retrospectively analyzed. The cohort was divided into two age groups: ≥4 years (n=102) and <4 years (n=20).Results. The mean PAS was lower among the younger compared with the older patients (5.3 and 6.6, resp.;P=0.005), despite the fact that younger children had more severe appendicitis (75.0% and 33.3%, resp.;P=0.001). PAS had low sensitivity in both groups, with a significantly lower sensitivity among the younger patients. Parent and doctor delay were confirmed in children <4 years of age with appendicitis. PAS did not aid in patients with doctor delay. Parameters in patient history, symptoms, and abdominal examination were more diffuse in younger children.Conclusion. PAS should be used with caution when examining children younger than 4 years of age. Diffuse symptoms in younger children with acute appendicitis lead to delay and to later diagnosis and more complicated appendicitis.