Major liver surgery requires accurate preoperative evaluation to balance the extent of resection with preservation of sufficient postoperative functional reserve and to minimize the risk of post-hepatectomy liver failure. Traditional clinical scoring systems, such as the Child–Turcotte–Pugh and model for end-stage liver disease provide useful prognostic information but lack the capacity to deliver quantitative or regional assessments of liver function. Quantitative nonimaging tests, including indocyanine green clearance and the methacetin breath test, measure global liver function but cannot determine regional variations, which are essential for complex resections. Imaging-based approaches, including volumetry, hepatobiliary scintigraphy, and quantitative magnetic resonance imaging techniques, have therefore emerged as alternative methods. Hepatobiliary scintigraphy, employing radiotracers, allows precise quantification of global and segmental liver function and is particularly valuable in patients with parenchymal disease or following augmentation procedures. Magnetic resonance-based methods, such as T1 relaxometry, dynamic contrast-enhanced, and multiparametric protocols, show considerable promise but require further validation and standardization before widespread clinical adoption. The integration of volumetric and functional imaging improves surgical planning, optimizes patient selection, and reduces the risk of post-hepatectomy liver failure, particularly in borderline cases.