There is no authoritative data to show how long is the doubling time of lung metastases, and it is necessary to judge the doubling time according to the type of lung cancer. Generally, lung metastases mainly refer to intrapulmonary metastases of lung cancer, and its doubling time is in 1~6 months; while the doubling time of lung metastatic carcinoma is in the tumor doubling time of about 30-400 days. Lung metastatic tumor doubling time refers to the time needed to double the volume of the tumor, if the patient presents with small-cell lung cancer, the lung metastatic tumor doubling time is usually around 1 month. If the patient presents with squamous lung cancer, large-cell undifferentiated carcinoma, large-cell carcinoma, the doubling time of lung metastases at this time is 3 months. Besides, if the patient develops lung adenocarcinoma, the doubling time of lung metastases is longer, at 4~6 months. It is suggested that patients with lung metastases need to have chest CT examination in time, and doctors will judge the type of lung cancer according to the multiplication time of lung metastases. It is generally believed that the tumor multiplication time is 30~400 days, so the multiplication time of lung metastases is also within this range. It is suggested that patients need to seek medical treatment in time when they develop lung metastases, and doctors will judge the doubling time of lung metastases according to the examination results. If a patient has a lung metastasis that multiplies too fast, he or she needs to choose appropriate measures for treatment under the guidance of a doctor, and he or she should ensure enough rest during the treatment period.