BACKGROUND Indocyanine green (ICG) elimination is a test widely used to evaluate hepatic functional reserve in patients being assessed for hepatic resection. This study compares a non-invasive liver function monitoring system, the LiMON (Pulsion Medical Systems, Munich, Germany), with serial blood sampling methods. METHODS ICG elimination was measured by the LiMON, spectrophotometry and high-performance liquid chromatography (HPLC) in 20 patients with hepatocellular carcinoma and cirrhosis as part of their preoperative work-up. RESULTS The ICG 15-min retention rates obtained by spectrophotometry and HPLC correlated well (correlation coefficient = 0.91), and there was good agreement between the tests (mean bias = 2.93, 95% confidence interval (CI) = 1.59-4.28). There was a reasonably strong correlation between results obtained with the LiMON and spectrophotometry (correlation coefficient = 0.81), and again there was good agreement between the tests (mean bias = 2.71, 95% CI = 0.19-5.22). On average, 15-min retention rates measured by the LiMON were 2.71 lower than those measured with spectrophotometry. CONCLUSION In patients being assessed for suitability of hepatic resection, the LiMON provides results similar to those obtained by serial blood sampling methods. This is important as techniques of carrying out ICG elimination vary widely between institutions and results are frequently incorporated into scoring systems that are used to determine surgical decisions.