PURPOSE: Abdominal CT scans in patients with intraperitoneal fluid were retrospectively studied to identify characteristic features useful for differential diagnosis of various causes. MATERIALS AND METHODS: One hundred and seventy patients with intraperitoneal fluid collection were classified as categories of hepatic disease, carcinomatosis, and infectious disease. We analyzed sites of fluid collection, the presence of peritoneal thickening, omental and mesenteric fat infiltration, and lymph node enlargment. RESULTS: Intraperitoneal fluid was present in subhepatic space, subphrenic space, paracolic gutter, mesentery, and fossa of the gallbladder in decreasing order of frequency. Fluid in the gallbladder fossa was the most frequent in hepatic diseases. The fluid collection in subhepatic and subphrenic space was less frequent in infectious diseases. Peritoneal thickening was noted in infectious diseases, and carcinomatosis. Omental fat infiltration and enlarged lymph nodes were the most frequent in carcinomatosis (58% and 44%, respectively), whereas, mesenteric fat infiltration and enlarged lymph nodes were the most common in infectious diseases (61%, and 26%, respectively). CONCLUSION: The location of peritoneal fluid collection showed some lesion specific characteristics, and CT features of fat infiltration and enlarged lymph nodes of peritoneum, omentum, and mesentery were helpful for differential diagnosis between carcinomatosis and infectious diseases.