Made an attempt to justify a separate direction of onkopsichology as independent scientific trend in this article. The results of a research diagnostic PTSD in breast cancer (BC) patients and determination of the relationship between intensity of post-traumatic stress symptoms (PTSD), EEG reactivity and immunity suppression is presented. The diagnosis of PTSD was made with the help of the psychometric methods (CAPS, MS, IOES-R, BDI, WAS, LEQ, SCL-90-R, ERP recording). The immunological status of patients was evaluated on the basis of 20 parameters. In this research have shown that BC happens to be a traumatic stressor that can cause PTSD: the condition that fits the clinical picture PTSD has been found in 24% of patients. Results of ERP recording reflect a presence of two factors that correlate with intensity of PTSD signs. PTSD group has significant profound immune alterations. The percentage of PTSD (24 %) in breast cancer patients does not much differ from those in traumatic events survivors (combat veterans, natural and technological disasters and accidental victims). This results received by the described approach reflect psychological problem situations existing among BC patients. These data can be helpful for psychological assistance and social rehabilitation of such patients. The issue of direct impact of stress on the origin and development of cancer need further investigation but so far there is evidence that intense post-traumatic reaction, which are observed in some BC-patients, can aggravate the course of the oncological disorder and influense negatively the patients'status, thus enhancing the risk of relapse.