Liver transplantation is an effective method for the treatment of hepatocellular carcinoma (HCC). In order to reduce the high recurrence rate of tumor after liver transplantation for HCC, some scholars put forward the famous Milan criteria. Since the Milan criteria are too strict, some HCC patients with relatively “good biological behavior” and large lesions or multiple nodules are excluded from the waiting list for liver transplantation, and thus a large number of “expanded versions of the Milan criteria” appeared around the world. As for the histopathology of HCC, microvascular invasion (MVI) and poorly differentiated tumor tissue are significantly associated with the high recurrence rate after liver transplantation for HCC. This article reviews and summarizes the articles on the application of 18F-FDG PET/CT in liver transplantation for HCC in China and foreign countries and points out that the uptake of 18F-FDG in HCC lesions reflects the difference in the biological behavior (i.e., invasion) of tumor tissue. The intense uptake of 18F-FDG is positively correlated with MVI and poor differentiation of HCC. In addition, 18F-FDG can detect extrahepatic metastatic lesions sensitively and accurately. Preoperative 18F-FDG PET/CT findings have a high value in predicting the prognosis of liver transplantation for HCC, and it is a trend to incorporate such findings into the criteria for liver transplantation in HCC. It is also expected to unify the various expanded versions of the Milan criteria. The new criteria for liver transplantation may be defined as follows: the Milan criteria should be followed in general; as for the patients who do not meet the Milan criteria, liver transplantation can be performed for those who have lesions with negative 18F-FDG PET/CT results, without the involvement of major blood vessels or extrahepatic metastasis.