The severity of a 12mm lung nodule depends on the cause of the disease and the test results. Infection or trauma will not be very serious; if it is a tumor, it is more serious and needs to be taken seriously. If a 12mm lung nodule is caused by a lung infection such as pneumonia or tuberculosis, or by trauma, and the test results show that the nodule is smooth and has no signs of malignant development, it is generally not serious. However, if the morphology of lung nodules is abnormal, and the examination results show abnormal manifestations such as burr-like and cavities, attention should be paid to assessing the shape of nodules, density value, lobulation, burr, pleural pulling signs, etc., and combined with the comprehensive analysis of the history of smoking and family history of tumors, etc., comprehensive treatments, mainly surgery, are feasible for those who have confirmed the diagnosis of malignant nodules or are highly suspected of malignant lung nodules. When lung nodules appear, it is necessary to actively consult the doctor to clarify the cause of the disease and then carry out targeted treatment.