The association between the Abernethy malformation, a rare vascular anomaly in which the portal blood is diverted into the systemic circulation, and development of hepatic tumours is well established. We present a case of multifocal hepatocellular carcinoma (HCC) in the presence of extrahepatic portosystemic shunt with a diminutive portal vein (Type 2 Abernethy malformation). Abdominal ultrasound performed on a 72-year-old female presenting with elevated liver function tests found a 5.6 cm right hepatic lobe mass. Subsequent CT and MRI examinations demonstrated multifocal lesions. A diminutive portal vein was present (transverse diameter of 7 mm) with a large tortuous complex shunt (maximum transverse diameter 2.0 cm) arising at the portal vein bifurcation with branches connecting to the left renal vein and inferior vena cava. Review of a CT examination performed 10 years ago demonstrated a normal-sized portal vein (transverse diameter of 1.5 cm) with a smaller calibre portosystemic shunt (maximum transverse diameter 9 mm). To our knowledge, this is one of the first reports to demonstrate the evolution of progressive portosystemic shunting and the development of HCC.