To the Editor : The most common cause of acute abdomen in children is acute appendicitis (AA); but its diagnosis presents significant difficulties so that early clinical diagnosis is often not straightforward [1]. Many studies have revealed clinical and laboratory signs of appendix perforation in children with more than 48 h delay of diagnosis after AA onset. However, the possible reasons for the delay in diagnosis of AA in children have not been clarified [2, 3]. We conducted a retrospective analysis of 378 children operated on for AA in our department between January 2007 and July 2013. The time that elapsed from the onset of symptoms to the surgical intervention was correlated with the following factors: age, obesity, use of antibiotics prior to diagnosis, and the initial examination by a pediatric surgeon or other physician. In less obvious cases, the patients underwent ultrasonography. Univariate and multivariate logistic regression analyses were performed. The diagnosis of AA was delayed by at least 48 h in 205 patients (Group A, 54.2%) and was made within 48 h in 173 patients (Group B, 45.8%). In Group A, 72 children were younger than 5 y, 53 were obese, 48 had received antibiotics and 146 were initially examined by a non-pediatric surgeon. Each of the examined factors separately significantly affected the diagnostic delay: age ≤ 5 y, p < 0.001; obesity, p < 0.05; using antibiotics, p < 0.001; and initial examination by a non-pediatric surgeon, p < 0.05. The percentage contribution to the delay increased or remained stable when two or more factors were combined, and it was 92.3% when all the risk factors were combined. All the examined factors contributed significantly to the delay in diagnosing pediatric AA. When the factors were combined, the most powerful were a younger age (p < 0.001) and antibiotic treatment (p < 0.005) followed by obesity (p 0.0634) and the initial examination being performed by a non-pediatric surgeon (p 0.8146). Therefore, physicians examining children with abdominal pain must keep in mind the multiple causes of diagnostic delay that may exist alone or in combination, and which can lead to serious complications and lengthen the hospital stay.