Lung nodules with a diameter of 5 mm may be caused by old lesions, non-specific inflammation, infection, tumor, etc. Close follow-up, anti-infection treatment, anti-tumor treatment and other therapeutic measures may be needed. 1. Close follow-up: If the possibility of benign lesions is considered to be high, regular follow-up may be needed to review the chest CT, and once the lesion is found to be enlarged, malignant changes should be alerted and handled in a timely manner. 2. Anti-infection treatment: Combined with clinical symptoms and relevant examination results, if infection is considered to be the cause, antibiotic treatment with amoxicillin, cefixime and other antibiotics may be needed. Simple nodules can not blindly apply antibiotics. 3. Anti-tumor treatment: If lung tumor is considered, comprehensive treatment mainly based on surgery may be needed. Therefore, timely medical attention is needed to assess the condition, active pharmacologic and non-pharmacologic management, and close observation.