Hepatocellular carcinoma carries a high risk of invasion of the portal vein. Neoplastic and bland portal vein thrombi discrimination is of great clinical significance for determining the therapeutic approach, predicting survival, and assessing candidates for liver transplantation. 18F-FDG PET/CT may be helpful in discriminating between malignant and portal vein thrombi. We present the case of a 61-year old man who presented with hepatocellular carcinoma with portal vein involvement. 18F-FDG PET/CT has a role in differentiating malignant from benign portal vein thrombosis.