Hepatic hypodense foci are a manifestation of a localized lower density in the liver than in the surrounding tissue, and there are many diseases that can present this way. Many benign diseases and malignant diseases can appear. 1, liver cysts are a relatively common manifestation of liver hypodensity during the examination. The general size varies from a few millimeters to several centimeters. In special cases, some liver cysts can affect liver function or are large and located under the peritoneum of the liver and are at risk of rupture at any time. 2. Hemangioma of the liver is one of the most common low-density lesions of the liver. They appear isolated or multiple, and are more common in women. They can range in size from less than 1 cm to 10 cm. Large hemangiomas show different imaging features due to internal hemorrhage and fibrosis. Based on these unique features, CT or MRI is easy to detect and diagnose clearly. The risk of hemangioma mainly comes from bleeding after rupture. For larger hemangiomas or located at the edge of the liver, timely surgical intervention is still needed. 3. Some women will take birth control pills frequently, which can lead to a kind of local nodular hyperplasia with low density in the liver. Generally in this case, no special discomfort will occur and most of them do not need special treatment. 4.Among liver malignancies, hepatocellular carcinoma is the liver hypodense lesion with the most incidence. This disease can be single, multiple or densely distributed in the whole liver. This kind of liver hypodense lesion usually shows infiltrative growth. For accurate diagnosis, enhanced CT or MRI of the liver is usually recommended to improve the positive rate of diagnosis. This is a kind of tumor with high malignancy. Early stage is mainly treated by surgery, and in advanced stage patients, various palliative surgeries, radiotherapy, chemotherapy, interventions and other treatments can be performed to prolong life. The technological update of imaging equipment allows more liver diseases to be detected and easier to be clearly diagnosed. It is imperative not to panic when the disease is discovered, but to seek timely hospital consultation to clarify the type of disease and choose the appropriate treatment for different conditions.