Portal vein thrombosis (PVT) is observed in 10-20% of patients with liver cirrhosis, which is responsible for 20% of all PVT cases. The main pathogenic factor of PVT in cirrhosis is the obstacle to portal flow, but acquired and inherited clotting abnormalities may play a role. The formation of collateral veins allows many patients to remain asymptomatic and prevents the onset of clinical complications also in patients with totally occlusive PVT. Gastrointestinal bleeding, thrombosis of superior mesenteric vein and refractory ascites are typical manifestations of PVT. Instrumental diagnosis can be obtained by colour-doppler ultrasonography. Future studies should verify whether asymptomatic PVT worsens liver failure, or if its life-threatening complications reduce survival in patients with cirrhosis. Moreover, randomized controlled trials should clarify the potential effectiveness of anticoagulant therapy in the treatment of PVT.