Background: High incidence and mortality rates of gastric cancer cause a constant search for the most informative and effective methods of diagnosis and treatment assessment. In this regard, studying the expression of markers with the stem phenotype in primary tumor tissues in patients with gastric cancer with and without metastases is of undoubted interest. Methods: The study included 20 gastric cancer patients aged 30-80 years: group 1 – gastric cancer T3-4аN0-3M0 (G2) without metastasis (58.9±9.7 years); group 2 – gastric cancer T3-4аN0-3M1 (G2) with peritoneal metastasis (53.4±11.9 years). Immunohistochemical study was performed on paraffin-embedded tumor tissue sections using mouse monoclonal antibodies to CD44 (156-3С11 Thermo Scientific) at a 1:2500 dilution and rabbit polyclonal antibodies to CD133 (Cloud-Clone Corp.) at a 1:700 dilution; the Thermo Scientific autostainer was used for staining. Membrane staining and staining intensity were assessed: 0, 1+ weak, 2+ moderate, 3+ strong staining. Positive expression was defined as ≥10% cut-off for CD44 and ˃5% for CD133. Results: Positive expression of CD44+ was detected in 67% (13) in group 2 vs. 20% (4) in group 1. In the metastatic group, the number of cells that stained positive for CD44 expression ranged from 9 to 15%, on average 10.0±3.08%, without metastases – from single cells to 13%, on average 6.0±2.3%. A chi-square test showed statistically significant association in the groups (8.256 at p = 0.004). Positive CD133+ expression in tumor tissues was registered in 100% (20) in group 2 and 80% (16) in group 1. The range of positively stained cells in group 2 was from 10 to 40%, on average 21.3±11.6%, in group 1 - from single cells to 14%, on average 10.0±2.4%. A chi-square test showed statistically significant association in the groups (4.444 at p = 0.036). Conclusions: Immunohistochemical study of the selected tumor cell markers in gastric cancer revealed some characteristics of their expression depending on the presence of metastases. The results can be the basis for further research for the most complete characterization of a heterogeneous tumor population in gastric cancer and the role of individual cells in the tumor growth, progression and metastasis.