PURPOSE: The purpose of this study was to evaluate the CT findings of parasitic ectopic infestation in theperitoneal cavity, a transitional route for parasites invading the gastrointestinal tract, to migrate to varioustarget organs. MATERIALS AND METHODS: CT scans of nine patients with pathologically(n=8) or serologically(n=1)proven intraperitoneal involvement of parasitic infestation were retrospectively reviewed. The primary causes ofparasitic infestation in nine patients were Paragonimus westermani(n=5), Sparganosis(n=2), and hepaticfascioliasis(n=2). We analyzed the CT findings with regard to the sites and patterns of lesions in the peritonealcavity and gastrointestinal track, as well as in other solid organs. The clinical features of these patients werealso evaluated. RESULTS: The clinical symptoms and signs were chronic abdominal pain and general weakness inseven patients, while peripheral blood eosinophilia was observed in four. The CT features of these nine patientsincluded multiseptated cystic masses of 2 -6cm, diameter (mean 4.1 +/-1.7cm) in the omentum or mesentery insix(67%), omental or mesenteric infiltration in seven(78%), focal peritoneal thickening in seven(78%),lymphadenopathy in five(56%), and ascites in four(44%). In six of the nine patients, the gastrointestinaltract(stomach in four, colon in one, both stomach and colon in one) was concomitantly involved with focal wallthickening. Branching patterns of hypoattenuating lesions were noted in the liver of three patients ; two of thesehad hepatic fascioliasis and one had paragonimiasis. CONCLUSION: Ectopic parasitic infestation in the peritonealcavity manifests as mass formation, adjacent gastrointestinal wall thickening, and focal peritonitis. Anunderstanding of these image features is important for both early diagnosis and adequate treatment.