Background/Aim: The P300 component of Event-Related Potentials (ERPs) is related to fundamental aspects of cognitive functions, such as Working Memory (WM) and attention allocation. Deficits in these domains have been implicated in the pathophysiology of depersonalization-derealization (DD). The present study focused on the P300 elicited during a WM test in transient DD experiences. Methods: Fifteen subjects with transient DD experiences were matched for age, sex and educational level to an equal number of healthy controls. Both groups were submitted to a computerized version of the digit span Wechsler batteries. P300 was measured during the anticipatory period of this test. All participants completed the Dixon self-rating questionnaire. Results: In relation to the control group, the subjects with transient DD experiences showed significantly decreased amplitudes of P300 at central posterior brain areas. Concerning memory performance, the groups did not differ significantly. Conclusions: These findings may indicate that subjects with transient DD experiences manifest altered aspects of information processing, as reflected by P300 amplitudes elicited during a WM test. Additionally, P300 might serve as a valuable investigative tool for a more comprehensive understanding of the neurobiological substrate of DD.