Can not be based solely on the size of the nodule to determine whether the seriousness of the lung 13 mm nodules, the need to first clarify the nature of the nodule, and then determine the severity of the disease. Lung nodules are focal, rounded lung shadows less than 30mm in diameter. Lung 13mm nodules can be caused by infectious lung lesions, benign tumors, malignant tumors and other diseases. Further investigations, such as enhanced CT of the lungs, bronchoscopy or lung puncture, are recommended to clarify the nature of the nodule. If the test results suggest benign lesions, the condition is relatively not serious and can be treated for the disease. If it is caused by an infection, it can be treated aggressively with anti-infective therapy. If the disease is caused by chronic inflammation or a benign tumor, the size of the nodule can be followed up periodically. If the test result suggests malignant lesions, the condition is relatively serious and requires surgical treatment, etc. under doctor’s evaluation. It is recommended that patients with 13 mm nodules in the lungs cooperate with the doctor to improve the examination and determine the nature of the nodules before deciding on the next step of the treatment plan.