The article is devoted to the analysis of actual scientific views and theoretical research on the participation of the phenomena of dissociation, splitting, and compartmentalization in disorders associated with mental trauma, in particular, PTSD and addictions. It is shown that the understanding of the concepts of dissociation and splitting developed in parallel and that both concepts emerged from research on trauma. Empirical studies show a clear correlation between dissociation, splitting, and compartmentalization with trauma-related disorders. However, there is considerable confusion in the differentiation of these concepts: some authors use them as synonyms, other authors consider dissociation to be a more basic process underlying splitting, and some distinguish two separate types of dissociation - separation, and compartmentalization. In this article, the concept of dissociation and splitting into separate independent phenomena is chosen, where dissociation is defined as the separation of mental processes or mental systems from consciousness, and splitting is defined as the division of consciousness itself into several independent centers of self-consciousness, with the phenomenon of compartmentalization referring to a shallow level of splitting. Both dissociation and splitting can exist in the spectrum from normal to deep pathology of the (sub)psychotic level. The article analyzes how dissociation and splitting can participate in the formation of trauma-related disorders such as PTSD and addiction. In the formation of PTSD, a part of the human psyche system associated with traumatic experiences is detached from consciousness as a result of protection from unbearable experiences (dissociation). Further, due to unsuccessful attempts to integrate the trauma, a negative self-concept with feelings of shame/guilt is formed, which splits off from the core self (splitting). As a result, a triadic structure is formed: the normative Ego-state, the split traumatic Ego-state, and the dissociated traumatic Self-state. When addiction is formed based on early trauma, a dissociated self-state exists since childhood, but while using psychoactive substances, it is integrated with a state of altered consciousness, which is why a person is experiencing a state of high, similar to a miracle. In this case, a system is formed of a normative Ego state, a dissociated traumatic Self-state, and a detached addictive Ego state, which is activated exclusively in a state of altered consciousness, and during activation, integration with the dissociated Self-state occurs. This addictive integration is the real motive for the use of this group of addictive drugs. The proposed concept can be used in the psychotherapy of trauma-related disorders as a conceptualization of cases and conceptualization of loci of therapeutic contact. Keywords: dissociation, splitting, compartmentalization, mental trauma, PTSD, addiction