Aim: to evaluate diagnostic value leucocyte count, percentage of neutrophil count and CRP levels in detection of acute appendicitis in children. Methods: We prospectively studied 112 consecutive patients, aged 0-15 years, who were referred to the outpatient pediatric department of our hospital with symptoms and signs of acute appendicitis, with intervals of less than 7 days from the onset, between October 01, 2010 and September 30, 2011. Predictors were values of leucocyte count, percentage of neutrophil count and CRP levels . Outcome measure was the PHD confirmation of acute appendicitis. Appendicitis-specific clinical and laboratory findings were done. Results: We found a significant difference between the values of leukocytes to the PHD group findings (F = 17.46, df = 3, p <0.001). There were significant differences in the values of neutrophils by PHD diagnostic categories between groups of subjects (F = 18.87, df = 3, p <0.001). Values of C-reactive protein also in comparison between groups divided according to the findings of the PHD appendectomy, showed a statistically significant difference between groups (ANOVA, F = 13.67, df = 3, p <0.001). Conclusion: In this study has been shown that Leucocyte count, C-reactive protein and neutrophil count are helpful tools to support the clinical diagnosis of all stages of appendicitis especially phlegmonous and perforated appendicitis in childhood.