Introduction and objective. Colorectal cancer is one of the most common cancers worldwide. In Poland, it is the second most common cancer, regardless of gender. The aim of study was to analyze the incidence of HPV and BKV in the tissue of colorectal cancer and to determine the relationship between the presence of these viruses and the development of this cancer. Materials and method. The experiments were conducted using 50 colorectal cancer tissues collected from histological sections. The clinical material was embedded in paraffin blocks. Next, DNA extraction was performed. Isolates of colorectal cancer tissue were tested for the presence of HPV DNA. BKV DNA was detected by PCR using specific primers and then differentiated from JCV by digestion with BamHI enzyme. Results. In clinical specimens taken from patients with colorectal cancer, HPV DNA was detected in 20% of cases. In 10% of cases the presence of HPV type 18 was confirmed, in the other 90% of the samples HPV type 16 was detected, while the presence of BKV was confirmed in 30% of cases. Coinfection with HPV and BKV was shown in 12% of patients. In one case, BK virus coexisted with HPV type 18, in the remaining 5 cases with HPV type 16. Conclusions. Developing colorectal cancer can show no symptoms, even for many years. This is why it is so important to become familiar with as many etiological factors as possible. The development of many human neoplasms is often initiated by exposure to infectious agents -such as bacterial or viral infections. Similar to the human papillomavirus, the BK virus was detected in clinical specimens. It seems that HPV and BKV infections can contribute to the neoplastic process, which requires detailed studies on a larger group of patients.