Background and Aims For colorectal cancer patients with and liver metastases and resectable lung metastases, surgical treatment has been widely accepted as an effective method. However, the treatment strategy for those with unresectable lung metastases still needs to be further specified. Therefore, this study was performed to retrospectively analyze the clinical data of colorectal cancer patients with simultaneous liver and lung metastases treated in the authors' hospital, so as to provide data reference for the treatment of these patients.Methods Using a retrospective cohort method, the data of 127 patients with colorectal cancer and simultaneous liver and lung metastases undergoing surgical treatment in the Department of Hepatopancreatobiliary Surgery Unit I of Peking University Cancer Hospital from January 2008 to December 2020 were collected. Of the patients, all cases underwent complete gross resection (R₀/R₁) of the primary lesions and liver metastases following the principle of tumor radical surgery, and 31 cases received radical local treatment of the lung metastases (local treatment group), while 96 cases did not receive local treatment of the lung metastases (non-local treatment group). The clinical variables, overall survival (OS) and recurrence-free survival (RFS) of the two groups of patients were compared, and the prognostic factors for patients in non-local treatment group were also determined.Results Except that the diameter of the lung metastases in local treatment group was larger than that in non-local treatment group (P<0.05), all other clinical variables showed no significant difference between the two groups (all P>0.05). The median follow-up time for the entire group of patients was 30 (5-134) months, and the rate of lost to follow-up was 3%. For the whole group, the median OS was 41 (4-118) months, and the 1- and 3-year OS rate were 96.8% and 59.7%, in which, the median OS and the 1- and 3-year OS rate were 37 (4-118) months and 95.8% and 51.2% for non-local treatment group, and were 72 (15-101) months, and 100.0% and 82.9% for local treatment group, respectively. The OS was significantly better in local treatment group than that in non-local treatment group (P=0.001). The median RFS was 8 (1-37) months, and the 1- and 3-year RFS rate were 30.8% and 2.4% for non-local treatment group, and the median RFS was 10 (3-67) months, and the 1- and 3-year RFS rate were 38.7% and 18.1% for local treatment group. The RFS was better in local treatment group than that in non-local treatment group, but the difference did not reach a statistical significance (P=0.055). The results of prognostic analysis in the 96 patients in non-local treatment group showed that T4 stage of primary tumor and RAS gene mutations were independent risk factors for OS (both P<0.05), and the median OS in patients with two risk factors were inferior to those with 0 or 1 risk factor (both P<0.05), but their median OS still approached 27 (4-35) months.Conclusion For patients with colorectal cancer and simultaneous liver and lung metastases, surgical resection of the primary lesions and liver metastases combined with local treatment of the lung metastases should be aggressively performed. For patients whose lung metastases cannot be treated locally, irrespective of whether or not they have risk factors, surgical treatment of the primary colorectal cancer and liver metastases may also provide a survival benefit.