Pseudomyxoma peritonei (PMP) is a rare, progressive disease of unknown origin. The incidence is estimated at about 1-2/100,000,000 per year. The primary tumor site is usually discovered in the appendix or- in case of women--in ovaries, appearing as tumors of low malignancy. Making an accurate diagnosis causes difficulties--symptoms tend to be misleading, suggesting more frequent pathologies of the abdominal cavity. It is also not rare that the patient is for a long time asymptomatic. We present a case of a 68-year-old patient of the Surgical Oncology Department treated for pseudomyxoma peritonei, diagnosed incidentally at the time of clinical examination for the reasons of chronic hypertension. The symptoms reported by the patient did not suggest any neoplastic process of the peritoneal cavity. Systemic chemotherapy of two paths (a total number of 10 cycles) did not result and at the time of post-treatment control, due to no response to standard chemotherapy, it was decided to administer chemotherapy intraperitoneally in hyperthermia (HIPEC). During the operation, peritoneal cytoreduction prior to the scheduled HIPEC was performed; the right-sided inguinal hernia was repaired. Within the hernia sac the implanted myxoid cells were found, their presence inside was probably the main reason of clinical manifestation of the disease.