Hepatocellular carcinoma (HCC) is the third most common cause of cancer deaths in the world. There have been many advances in the diagnosis of HCC during the last ten years, especially in the imaging techniques. The Korean Liver cancer study group (KLCSG), European Association for the Study of the Liver (EASL), American Association for the Study of Liver disease (AASLD), and Asian-Pacific Association for the Study of Liver (APASL) have made and changed the HCC guidelines with the advances in the imaging techniques and according to the results of the researches on HCC. We reviewed the changes of the imaging guidelines in HCC diagnosis according to the advances in the imaging techniques. Further studies will be necessary to resolve the controversies in the diagnosis of HCC smaller than 1 cm in size.