The aim of this study was to enhance our understanding of the pathways of lymphatic spread of primary carcinomas in the upper abdomen by recognizing the development, configuration, and frequency of nodal enlargement in discrete anatomic regions. The study included 417 patients with histologically confirmed carcinomas (CC) of the stomach (n = 267), liver (n = 98), gallbladder (n = 25), and bile ducts (n = 27). All patients were studied by high-resolution CT and tumor extension to the lymph nodes of the subperitoneal space was clearly identified in 59 patients [33 with CC of the stomach, 8 with CC of the gallbladder, 3 with CC of the bile ducts, and 15 with hepatocellular carcinoma (HCC)]. In 47 of 59 patients this extension was confirmed by surgery or aspiration biopsy. Three discrete anatomic groups of lymph nodes were recognized producing a relatively distinct CT configuration when involved: (a) the hepatoduodenal seen in 49 patients; (b) the peripancreatic demonstrated in 33 patients; and (c) the aortocaval recognized in 16 patients. These groups of lymph nodes can be seen individually involved or in combination. Recognition of involvement of these nodes is important for correct diagnosis and staging of upper abdominal malignancies. The development of this involvement follows the natural flow of lymph via the lesser omentum to the retroperitoneal space.