Primary peritoneal cancer and mesothelioma belong to one nosological structure namely primary malignant neoplasms of the peritoneum. Such pathologies, regardless of their morphological differences, have the following in common: low incidence, the absence of pathognomonic signs, similarity of radiological signs and lack of knowledge regarding prognostic factors. Considering the low incidence, reliable differential diagnostic indicators are not currently set up, which makes it substantially more complicated to timely formulate the diagnosis. On the contrary, more often we could reveal the cases where the wrong treatment strategy has been chosen, the absence of unified maintenance algorithm, when in fact a history of a patient`s present illness represents an individual creation of a particular doctor. On the other hand, the independent experience of a number of clinics does not exceed a few observations, which does not allow doctors to confidently navigate the problem. Thus, the relevance of conducting multicenter and perhaps prospective randomized scientific research studies with the aim of unified algorithm elaboration of the management of patients with primary peritoneal neoplasms has become imminent. The traditional algorithms for this pathology treatment embrace surgical step and systemic or intracavitary chemotherapy, where treatment sequence could be varied and foremost depends on a disease spread. In order to determine the extent of intraperitoneal dissemination the Sugarbaker peritoneal carcinomatosis index (PCI) is currently used, it also has been proved that one of the main prognostic factors is the degree of cytoreduction completeness. In the article below, we have tried to provide modern concepts of primary peritoneal cancer and peritoneal mesothelioma diagnosis, treatment and prognosis.