PURPOSE: To evaluate the CT findings of patients with surgically confirmed perforated appendicitis and to compare the characteristics between children and adults. METHOD AND MATERIALS: Patients in whom complicated appendicitis was clinically suspected underwent contrast enhanced CT scanning. The scans of 50 patients (19children and 31 adults) with surgically confirmed perforated appendicitis were analysed. Without knowledge of operative findings, we retrospectively analyzed the CT findings with regard to : 1) the detection of the appendiceal wall thickening; 2) the presence of appendicolith; 3) the size, features, and location of periappendical abscess; 4) mesenteric fat infiltration and lymphadenopathy; 5) wall thickening of the cecum and terminal ileum; and 6) ascites and free air. RESULTS: Appendiceal wall thickening was detected in seven children(37%) and 13 adults (42%) (p>0.05). Appendicolith was detected in 21 patients (42%) and was more frequent in children (13 cases, 68%) than in adults (8 cases, 26%). There were statistically significant differences between the two groups (p<0.05). The mean diameter of periappendiceal abscesses was 3.7+/-1.9 cm (3.2+/-1.9 cm in children and 4.0+/-1.8 cm in adults), with no stastistically significant differences between the two groups (p>0.05). Periappendiceal abscess with well-defined cyst was more frequent in children (17/19, 89%) than in adults (13/31,42%) (p<0.05). The most commonly involved site was the midabdomen and pelvis in children (9/19, 47%), and the right lower quadrant in adults (18/31, 58%), (p <.05). Mesenteric lymph nodes were commonly detected in children, and cecal wall thickening in adults. CONCLUSION: The CT findings of perforated appendicitis included appendiceal wall thickening, appendicolith, periappendiceal abscess, mesenteric fat infiltration and enlargement of mesentericlymph nodes, and thickening of the cecum wall Periappendiceal abscess with well-defined cyst in the midabdomen or pelvis was more frequent in children, as were appendicolith and enlargement of mesenteric lymph nodes.