Colorectal cancer is a disease whose prevalence has been steadily increasing in recent years. It is asymptomatic in early stages, which is why early detection is essential for improving prognosis and reducing mortality. Due to the invasiveness and limitations of colonoscopy and tissue biopsy as existing diagnostic methods, liquid biopsy was developed as an innovation in the field of oncology. It is a non-invasive and reproducible method by which it is possible to isolate exosomes from the patient's peripheral blood. Exosomes carry molecules originating from tumor tissue with potential to be used in disease monitoring, one of them being TGF-ß1. Mutations in TGF-ß1 signaling path affect cell proliferation, tumor progression and development of metastases. The aim of this thesis was to determine the presence of TGF-ß1 in exosomes from patients with colorectal cancer obtained by liquid biopsy and to compare it with the results of immunohistochemical analysis of tumor tissue obtained by biopsy. Using liquid biopsy, exosomes were isolated from plasma samples of patients with colorectal cancer. The protein concentration in all samples was determined by spectrophotometric method with bicinchoninic acid and Western blot analysis was performed. The presence of TGF-ß1 was proven in all samples, with relative quantification of the obtained results. Immunohistochemical analysis of tumor tissue obtained by biopsy also demonstrated the presence of TGF-ß1 in all samples. In conclusion, results obtained by liquid biopsy are identical to those obtained by tissue biopsy. The above, along with the necessary further research, allows liquid biopsy to be introduced into clinical practice as a non-invasive method that enables high-quality screening, diagnosis and disease monitoring in patients with colorectal cancer.