Multiple nodules of 3 to 5 millimeters in the lungs are multiple pulmonary nodules. According to the nature of the nodules, they can be categorized into benign and malignant pulmonary nodules. The severity of the disease needs to be judged according to the nature of the nodule and whether it is treated in time, etc. Generally, benign lung nodules have a better prognosis after active and effective treatment, while malignant multiple nodules are more serious and usually have a poorer prognosis. The majority of patients with multiple 3-5 mm nodules in the lungs may have no obvious symptoms and are usually found incidentally during physical examination, while some patients may have symptoms such as cough, hemoptysis, chest pain and dyspnea. Benign pulmonary nodules may be caused by pulmonary fibroma, infection, nodular disease, etc. Generally, after timely, reasonable and standardized treatment, the prognosis is better. For example, multiple pulmonary nodules caused by tuberculosis, can follow the doctor’s instructions to use isoniazid and other drugs to kill tuberculosis bacilli; infected pulmonary nodules commonly used oxyfloxacin, erythromycin and other antibiotics, anti-infective treatment, most patients can be cured. As for malignant lung nodules, most of them are primary lung cancer, which has a rapid course and strong malignancy, then it causes serious lung function damage and generally has a poor prognosis. When the imaging examination suggests that there are multiple nodules of 3~5 mm in the lungs, the patient should consult the doctor in time for judgment and appropriate treatment if necessary.