Polyunsaturated fatty acid (PUFA) deficiency occurs in advanced cirrhosis and other liver diseases (acute hepatitis, cholestasis). Long-chain PUFA deficit in cirrhosis is due to both essential fatty-acid (EFA) deficiency and impaired PUFA biosynthesis. Although hepatic insufficiency itself mostly accounts for this phenomenon, other factors such as associated malnutrition also play a role. PUFA deficiency in cirrhosis probably has a wide array of both cellular and clinical consequences, but, at present, they have been difficult to prove. In addition, the route, dosage, and safety of PUFA supplementation in these patients needs extensive investigation in the future.