The term "delusional misidentification syndrome" (DMS) includes undoubtedly the Capgras syndrome, the Fregoli syndrome, intermetamorphosis and the syndrome of subjective doubles. Until the past decade DMS was regarded as very rare, but an increasing number of cases are now being reported. A range of suggestions has been put forward in order to explain etiopathogenesis of DMS. Psychological and especially psychodynamic viewpoints attributed a decisive pathogenetic role to the defense mechanisms of splitting and projection. DMS was compared with a phenomenon of prosopagnosia. An attempt of theoretical explanations of DMS was information-processing model of familiar face recognition by Bruce and Young. Nowadays event-related potentials, especially auditory P300 component, constitute a useful tool providing valuable information with regard to the brain-behaviour relations.