PURPOSE OF REVIEW: Small-for-size syndrome (SFSS) is a clinical syndrome described following liver transplantation (LT) and extended hepatectomy. New evidence has emerged documenting the importance of preoperative evaluation of functional liver mass, liver quality, influence of portal hypertension, and variations in surgical technique to improve outcome. RECENT FINDINGS: SFSS is characterized by postoperative coagulopathy and liver dysfunction due to insufficient functional liver mass. Recent radiologic advances allow accurate preoperative estimation of total, graft, and remnant liver volume (RLV). In adult-to-adult living donor liver transplantation (LDLT), a graft-to-recipient body weight ratio > or = 0.8% or graft weight ratio > or = 30% are important to avoid SFSS. Minimal functional RLV following extended hepatectomy is > or = 25% in a normal liver, and > or = 40% with preoperative liver dysfunction. Preoperative portal vein or hepatic artery embolization to increase RLV and function after extended hepatectomy, and the increasing use of parenchymal-sparing segmental resections have improved outcome. In LT, the evolving use of split livers, LDLT and marginal grafts has resulted in increased recognition of SFSS. This has led to a renewed interest in defining the pathophysiology, and the development of new surgical techniques to reduce its incidence. SUMMARY: Current radiologic imaging techniques can be used to evaluate liver volume and the risk of SFSS following LT and extended hepatectomy. Intraoperative techniques to predict postoperative dysfunction are emerging, and may be helpful in directing the use of pre-emptive surgical interventions. The future lies in the development of perioperative liver protection and support in predicted SFSS, and enhancement of healthy liver regeneration.