Objective. The study objective was to assess the scintigraphy potential in the evaluation of portal hypertension and the severity of liver damage in diffuse diseases and after liver transplantation.Material and methods. The study enrolled 325 patients suffering from hepatitis and liver cirrhosis of various etiology and severity, including those after liver transplantation, namely, the patients with hepatitis (n=96), patients with liver cirrhosis of Child–Pugh class A (n=24), class B (n=87), and class C (n=118); 11 more healthy volunteers without clinical and laboratory signs of diffuse liver disease were enrolled as controls. The assessment of liver reticuloendothelial system was performed by scintigraphy with (99m)Tc-phytate colloid in a static planar mode and "whole body" mode by SPECT (Infinia II, GE).Results. In contrast to the control group, significant radionuclide signs of hepatosplenomegaly were revealed with the predominant functional activity of the left lobe; the liver function was found impaired that correlated with the cirrhosis severity evaluated according to the Child–Pugh Сlassification. The analysis of scintigraphy quantitative parameters showed that the most informative of them were the intensity of radiopharmaceutical accumulation in the spleen (S%) and in bone marrow (Вm%), and the radiopharmaceutical uptake by the reticuloendothelial cells of the liver and spleen in percentage from the administered activity (Lwb%, Swb%). Depending on the cirrhosis severity assessed by the Child–Pugh Score, the changes in quantitative parameters were accompanied by a progressive enlargement of the spleen, liver left lobe, the increase of (99m)Tc-phytate uptake by the bone marrow with a decreased radiopharmaceutical uptake by the liver. The study results showed that among the Child–Pugh class C patients, the impairment of liver reticuloendothelial function was more pronounced in the patients with cirrhosis of viral and mixed etiology, when compared to those with alcoholic cirrhosis.Conclusion. The paper has identified the most informative parameters characterizing portal hypertension and the reticuloendothelial function for all Child–Pugh defined classes of cirrhosis. These parameters include the increase of (99m) Tc-phytate accumulation in the spleen (S%) and bone marrow (Bm%); the liver and spleen uptake of the radiopharmaceutical in percentage from the administered activity (Lwb%, Swb%). The calculation of the remaining parameters is necessary for a detailed description of the organ function and for the assessment of the portal hypertension severity in repeated studies.Summary. Criteria for the objective assessment of reticuloendothelial function and portal hypertension in diffuse liver diseases, including after liver transplantation, have been developed. Contrary to the control group, in patients with diffuse liver diseases, the radionuclide signs of hepatosplenomegaly (or a decreased liver size) with a predominant functional activity of the left lobe were identified, as were the changes in the quantitative parameters of the radiopharmaceutical uptake by the liver (Lwb%), including the radiopharmaceutical accumulation in the liver left lobe (Ll%), spleen (Swb%), bone marrow (Bm%), and the liver-to-spleen area ratio (Lar/Sar). The informative and reliable (p<0.05) parameters of the function Lwb%, S%, Swb% and Bm% correlating with the cirrhosis classes assessed by Child–Pugh were identified. The radionuclide method, being highly reproducible one, can be recommended for an objective assessment of liver function and the detection of portal hypertension in hepatitis and cirrhosis, as well as for post-transplant monitoring of the liver function to prevent complications in the early and late postoperative periods.