High density shadow of 6mm in the lungs is not normal, and it is considered that the lungs have been infected and tumor. High density shadow in the lungs is a kind of imaging description of increased density seen in chest X-ray or CT examination, from the examination this density shadow has reached 6mm, it is considered that there may be infectious diseases in the lungs, such as pneumonia, tuberculosis, bronchial dilatation and so on. In addition, lung tumors can also appear in the lung hyperdense shadow, benign tumors have clear boundaries and no obvious adhesion with the surrounding tissues, if the edges of the hyperdense shadow are rough, malignant tumors may be considered, and it is necessary to further carry out the tumor series, sputum culture screening for cancer cells, etc., and if necessary, bronchoscopy biopsy can be done to clarify the pathological nature of the shadow. When 6mm high density shadow appears in the lung, it is recommended to go to the hospital in time to avoid delaying the condition.