Purpose: The study aimed at establishing the relationship between posttraumatic cognitions resulting from traumatic experiences as well as disruption in core beliefs and the level of symptoms of posttraumatic stress (PTSD). Another aim was to check whether the disruption of core beliefs is a mediator between posttraumatic cognitions and symptoms of PTSD.

Methods: Results obtained from 57 parents aged 25-57 years (M = 35.38, SD = 8.32), who have dealt with their child’s cancer (men – 47.4%; women – 52.6%) were examined. Three measuring methods were used in the study: the Impact of Event Scale-Revised (IES-R), Posttraumatic Cognitions Inventory (PTCI) and the Core Beliefs Inventory (CBI).

Results: The results showed positive associations between posttraumatic cognitions as well as disruption of core beliefs and the severity of PTSD. Challenges for core beliefs act as mediators in the relationship between posttraumatic cognitions and symptoms of PTSD.

Conclusions: The experience of a traumatic event usually entails the occurrence of posttraumatic stress symptoms. The severity of these symptoms is determined by, among others, the individual’s beliefs about the world and about themselves. The experience of a child’s cancer is a traumatic experience for parents. Negative cognitions and disruption in key beliefs favour the persistence of PTSD symptoms. Disturbances in beliefs are mediators in the relationship between negative cognitions and symptoms of PTSD. Reducing symptoms of PTSD, and thus recovery, requires a change in beliefs that are distorted by trauma.