Objective — to assess the impact of comorbidity on the incidence of postoperative infectious complications after major liver resections in patients with biliary obstruction Materials and methods. The study included 105 patients who were divided into two groups: Group 1 — 53 patients with biliary obstruction (7 with hepatocellular carcinoma (HCC), 28 with cholangiocarcinoma (CC), 18 with colorectal cancer metastases), Group 2 — 52 patients without biliary obstruction (25 with HCC, 10 with CC, and 17 with colorectal cancer metastases). The patients were statistically homogeneous in terms of age and gender. The age of patients in group 1 was on average 60.2±10.7 years, group 2 — 63.5±11.4 years. A microbiological study of 632 isolates of bile (before and after extensive resection), urine, blood, sputum, pharyngeal and wound samples (once) was performed. The bacterial cultures were identified using a Vitek MS mass spectrometry Aanalyser with MALDI‑TOF technology. Results. Patients with primary malignant and metastatic liver tumours and biliary obstruction have the following comorbidity associations: hypertension + heart failure, hypertension + heart failure + diabetes mellitus, hypertension + venous disease of the lower extremities + thrombophlebitis, hypertension + gastroesophageal reflux disease + chronic hepatitis, hypertension + hypothyroidism + metabolic‑associated steatotic liver disease; for patients with primary malignant and metastatic liver tumours without biliary obstruction — arterial hypertension + heart failure, arterial hypertension + heart failure + diabetes mellitus, arterial hypertension + gallstone disease, arterial hypertension + venous disease of the lower extremities + thrombophlebitis, arterial hypertension + bronchial asthma/chronic obstructive pulmonary disease, arterial hypertension + gastroesophageal reflux disease + chronic hepatitis. Conclusions. Biliary obstruction in the setting of comorbidity statistically significantly increases the resistance of Enterococcus faecium strains to cefuroxime, levofloxacin, Staphylococcus aureus — to meropenem, levofloxacin, Klebsiella pneumoniae — to meropenem, cefuroxime, rifaximin, Acinetobacter baumannii — to meropenem, cefuroxime, levofloxacin, rifaximin, Pseudomonas aeruginosa — to cefuroxime, levofloxacin, rifaximin, Enterobacter spp — to meropenem, levofloxacin, rifaximin.