Hepatocellular carcinoma is mostly a low-density shadow in CT, but it may also be a high-density shadow, which requires a comprehensive dynamic enhancement examination. Hyperdense and hypodense shadows are the examination results obtained by observing the lesion through imaging, which indicate the difference in density with the neighboring tissues. Hepatocellular carcinoma usually shows low-density shadow in CT, but some patients also have high-density shadow, so it needs to be judged by combining other manifestations. Imaging diagnosis of hepatocellular carcinoma is mainly based on the “fast-in-fast-out” enhancement mode of dynamic enhancement scan. In dynamic enhancement CT, the liver tumor in arterial phase shows uniform or uneven obvious enhancement, and the liver tumor in portal and/or delayed phase has lower enhancement than the liver parenchyma. “Fast-in” is non-circumferential enhancement and “fast-out” is non-peripheral contouring. “Fast in” is observed in the late arterial phase and “fast out” is observed in the portal and delayed phases. Scientific and comprehensive examination is needed to make a clear diagnosis of liver cancer and to know whether one is suffering from liver cancer. Clinical diagnosis of liver cancer can only be made through comprehensive assessment by imaging examination, pathological biopsy and blood test. Once diagnosed with liver cancer, it is recommended to receive treatment as soon as possible.