Delusional misidentification provides us with an excellent example of how it is necessary to take both organic brain disease and psychological processes into account when describing the development of mental symptoms. A model of delusional misidentification is proposed which was developed in an attempt to explain this interaction. The model is based on the events that occur during preconscious processing of perceptions. It predicts an inverse relationship between the presence of organic brain disease and the presence of paranoid delusions. This was tested using a retrospective analysis of case reports. A graded and inverse relationship between the degree of organic disturbance and the presence of paranoid delusions preceding the delusional misidentification was found. A satisfactory model of delusional misidentification syndromes must be able to acknowledge the way these two forces are able to interact.