Whether a 9mm lung nodule is serious or not mainly depends on the nature of the nodule, if it is malignant, then naturally the condition will be relatively more serious, because the deterioration of the disease may be life-threatening. A 9mm pulmonary nodule is a round or irregular nodular lesion with a diameter of 9mm found in the lung tissue when the organism is scanned by chest X-ray or CT scan. Lung nodules are imaging descriptions that do not identify the disease, and the severity cannot be assessed on the basis of the imaging nodules alone. It needs to be analyzed in conjunction with clinical symptoms and underlying disease. Lung nodules can be categorized into benign and malignant according to the type of pathology. Malignant lung nodules are lung nodules caused by lung cancer, or metastatic lung cancer caused by metastasis of malignant tumors in other parts of the body; whereas benign lung nodules are non-malignant tumors, and the common ones are pulmonary tuberculosis, pulmonary malignant tumor, pulmonary hemangioma, and pulmonary abscess. Malignant lung nodules are generally more difficult to treat than benign lung nodules, and the condition is relatively more serious. Individuals who are found to have 9mm nodules in their lungs should undergo further tests to clarify the diagnosis and find out the exact cause of the nodules, and then follow the doctor’s instructions to implement a standardized treatment plan.