Gastric cancer is one of the most common malignancies in the world and the third leading cause of cancer-associated death worldwide. Although the overall incidence of gastric cancer has declined rapidly over the recent few decades, increase in the incidence of the diffuse subtype is concerning in which, despite significant advances in diagnosis and treatment, no significant progress has unfortunately been made in finding an effective therapy. Although the pathogenesis of gastric adenocarcinoma is the subject of numerous studies, the molecular profile of diffuse gastric cancer is still a big mystery. The aim of this dissertation was to investigate changes in protein expression of Dishevelled family, Secreted frizzled-related protein (SFRP) and transcription factor TCF-1, the molecular components of the Wnt signaling pathway, in diffuse gastric cancers and compare results with pathological and clinical parameters. Immunohistochemical and stereological quantitative analysis of 62 samples of diffuse gastric cancer and 62 control samples of healthy gastric tissue revealed a statistically significant difference in the expression of SFRP1, SFRP3, TCF-1, DVL2 and DVL3 proteins. The expression of SFRP1, SFRP3 in tumor tissue was significantly lower compared to healthy tissue, while the expression of DVL2, DVL3 and TCF-1 was significantly higher in tumor tissue compared to healthy tissue. No statistically significant difference in expression was found for any of the proteins in relation to the clinical and pathological characteristics of the patients. The obtained results indicate a significant role of the Wnt signaling pathway components in the development of diffuse gastric carcinoma and represent the basis for further research.