Peritoneal diseases can be seen in the different imaging modalities either as fluid collections or solid tumors along the ligaments, mesenteries, and spaces of the peritoneal cavity. The broad spectrum of different abnormalities includes inflammatory, infectious, traumatic, and neoplastic diseases. In this article, a large variety of peritoneal abnormalities such as ascites, peritonitis, intraperitoneal hemorrhage, and both primary and secondary peritoneal tumors are discussed. The different imaging modalities, characteristic radiological features, and typical pathways of anatomic spread are explained.