Background: The term acute abdomen refers to the sudden onset of severe abdominal pain requiring urgent medical or surgical treatment. Objective: The aim of the present work was to compare the degree of current accuracy of abdominal ultrasound (US) and multi-detector row computed tomography (MDCT) in diagnosis of cases presented with acute abdomen in a child in Pediatric Assiut University Hospital, in order to optimize the radiologic diagnostic findings in relation to cost and time consumed. Patients and methods: This study was conducted retrospectively on 70 patients less than18 years old; 42(59.3%) males and 28 (40.7%) females. The mean age of participants was 9 (SD 3.63) years old. Those patients were presented to the emergency department (ED) in Pediatric Assiut University Hospital from April, 2017 to April 2018. Results: About 78% of cases presented by acute appendicitis; signs seen with US were matching to intraoperative findings, while 22% were not matching. Up to 70% of cases diagnosed as intestinal obstruction, a sign seen with US was matching to intraoperative findings, while 30% were not matching. Only 16.6% of cases diagnosed as perforated viscus, and signs seen with US were matching to intraoperative findings, while 83.3% were not matching. Only 3% of the participants in this study had non-diagnostic ultrasonography or a diagnostic dilemma. Conclusion: Although CT provides a diagnostic advantage over ultrasound, particularly in surgical instances, it should only be used in cases where the diagnosis is truly challenging due to radiation exposure risks. When acute appendicitis is suspected, the possibility of complicated appendicitis as in appendicular mass or abscess, or a perforated appendix should be excluded during US examination, otherwise plain MDCT is recommended.