Mixed density shadow of lungs 20mm can usually be treated with medication under doctor’s guidance, which is usually caused by bacterial infection, tuberculosis, lung tumor and so on. 1. Bacterial infections: Bacterial infections generally refer to a variety of bacterial, fungal infections, patients may have cough, fever and other symptoms, can be under the guidance of the doctor to use amoxicillin, levofloxacin and other drugs to carry out the treatment, for penicillin, quinolone allergy to patients with the use of this drug is prohibited. 2. Tuberculosis: Tuberculosis is generally caused by Mycobacterium tuberculosis, usually due to respiratory infection, digestive tract infections, etc. Patients can use pyrazinamide, ethambutol and other drugs under the guidance of a doctor for treatment, after the use of the patient may experience nausea, vomiting, diarrhea and other symptoms, optic neuritis patients are prohibited from using this drug. 3. Lung tumor: 20mm lung tumor may be benign or malignant, surgery is generally recommended, and the resection specimen should be sent to pathology, if it is benign, early resection should be performed to avoid malignant change, if it is malignant, lymph node clearance should be performed, and combined with radiotherapy, immunotherapy and other treatments after the surgery if necessary. Patients should go to the hospital for examination and treatment under the guidance of the doctor.