18mm lung nodule can be caused by infection, malignant tumor, chronic inflammation or benign tumor, etc. It can be treated with anti-infection therapy, surgical resection and regular follow-up. If the 18mm nodule is considered to be caused by infection, anti-infection treatment can be given, and the nodule can usually shrink or disappear after anti-infection treatment. If the nodule is a mixed ground glass nodule, or the nodule has a burr, or even has a vacuolar sign, then the possibility of malignant nodules should be considered. In this case, the nature of the lung nodule can be determined through bronchoscopy or CT-guided lung puncture biopsy to obtain pathological tissue. If the nodule is diagnosed as malignant, prompt surgical treatment is required. If the nodule is highly suspected to be malignant but pathologic tissue cannot be obtained by bronchoscopy or CT-guided puncture, the nodule can be directly resected thoracoscopically, followed by intraoperative rapid pathology. If intraoperative rapid pathology suggests malignancy, radical lung cancer surgery is required. If, after a series of tests, the result is a benign nodule, regular follow-up observation is an option. When 18mm lung nodules are found in the lungs, it is recommended to actively consult the doctor to clarify the cause of the disease and standardize the scientific treatment.