The purpose of this study was to evaluate the CT characteristics of metastatic pulmonary tumor. The study included 163 cases. Analysis of the distribution of 1265 metastatic nodules observed the conventional and helical CT with 10 mm slice thickness showed that they were distributed mainly below the carina and external peripheral lung field. The relationship between the characteristics of the margins of the metastatic nodules and primary tumors was evaluated in 280 nodules with high-resolution CT(HRCT). The margins were smooth in 88% of thyroid cancers, 85% of hepatocellular carcinomas and 75% of renal cell carcinomas, and irregular in 75% of pharyngolaryngeal cancers, 62% of colon cancers and 58% of breast cancers. HRCT findings were correlated with histology in 23 surgically resected metastatic nodules. The well-defined smooth margin on HRCT histologically corresponded to the expanding type, while the irregular margin corresponded predominantly to the alveolar space-filling type. Among other CT findings calcification was seen in colon cancer and osteosarcoma, and cavitation in pharyngolaryngeal cancer, colon cancer angiosarcoma, pancreatic cancer and endometrial uterine cancer. The author concludes that CT is useful for observing the morphologic features of metastatic pulmonary nodules which seem to reflect the underlying pathologic characteristics and thus contributes to the diagnosis.