We have experienced thirty-one operations of metastatic lung tumors from colorectal cancer. Various factors affecting prognosis are studied based on 5-year survival in this report. Overall 5-year survival rate was 32%. Statistical significance was present in the relationship between the prognosis and both maximum diameter of lesions and the disease free intervals (DFI) after surgery for metastatic lesions. Though not significant, sex, stage of primary lesion, nodal involvement, surgical procedure, postoperative serum CEA were likely affecting factors on the prognosis. In contrast, there were no relationship between the prognosis and following factors: age, location of the metastatic lesion, DFI after the operation for primary lesion and chemotherapy. Although pulmonary metastasis is essentially an index of the advanced state of malignant diseases leading to poor prognosis, long-term survivors were encountered in our series of surgical treatments for pulmonary metastases from colorectal cancers. It was concluded to be important to make efforts to extend the indication for surgical treatment, since the appropriate selection of patients revealed to give excellent results from our experience of colorectal cancer. In order to improve the prognosis, early detection of pulmonary metastases is quite important, since the incidence of nodal involvement proved to be higher in lesions with larger diameter resulting in inferior survivals from the present study. In addition, low incidence of nodal involvement in small-sized lesion may support possible applicability of thoracoscopic surgery in the excision of metastatic tumors locating at peripheral lesion.