Introduction. Primary mediastinal B-large cell lymphoma is non–Hodgkin's lymphoma, which is characterized by the development of a massive conglomerate of lymph nodes. The International Prognostic Index (MPI) is used as a prediction of the risk of early progression, but factors which are included there, doesn’t work with PMBCL. The aim. To develop a risk model for patients with primary mediastinal B-large cell lymphoma. Materials and methods. The study was included 47 patients with PMBCL, the overall survival was rated depending on clinical factors. Results. According to the statistically significant data, which are obtained on the effect of "B-symptoms", "bulky disease", respiratory failure, they were selected for developing a model of the risk of death of patients with PMBCL. Discussion. There is no association with lower survival of factors of IPI, the predominant using for diffuse B-large cell lymphoma, it is good to create a PMBCL-specific model of the risk of death of patients. Conclusions. A prognostic model of the risk of death of patients with PMBCL with high sensitivity and specificity was created.