In this thesis we have attempted to address the complex issue of the relationship between trauma, dissociation, and psychosis. It is hypothesised that dissociation, occurred as a result of trauma, plays a key role in the formation and maintenance of psychotic symptoms, chiefly hallucinations and delusions. We have used methods from experimental psychopathology to investigate the potential role played by dissociative processes in the disruption of the cognitive processes of attention and memory for trauma-related, positive and neutral information in two groups of participants: 30 individuals with psychosis and 30 matched controls. In particular, we used self-report measures of symptomatology, recovery style, trauma, and dissociation, and employed two experimental tasks. The first was specifically devised to assess attentional processes: a Directed Forgetting Stroop Task (DFST) performed under conditions of divided attention. The second task was a Word-Stem Completion Task (WSCT) on which we applied the process dissociation procedure (PDP; Jacoby, 1991) in order to estimate the relative contribution to dissociation of implicit and explicit memory. As expected, our findings revealed that the experimental group processed information preferentially in an implicit manner. Generally, the psychosis group exhibited a better memory performance for trauma-related information, better conscious retrieval inhibition for the same material, and more difficulty in forgetting it. We also found that our self-report measure of trauma predicted levels of dissociation, which, in turn predicted individuals’ recovery style. Additionally, both dissociation and recovery style predicted levels of positive symptoms. However, we did not find a standard directed forgetting effect on our memory task or an advantage (less interference due to dissociation) on our task of divided attention. Results are discussed in the light of the theoretical background, previous experimental literature, and current models of trauma and dissociation.