Personalization in psychiatry, among many other aspects, involves a precise diagnosis that describes the patient’s symptoms. Establishing an accurate diagnosis contributes to the implementation of appropriate therapeutic procedures. Nowadays, the rights of existence of some psychiatric diagnoses are denied. Chronic hallucinatory psychosis (psychose hallucinatoire chronique – PHC) is one of these mental illnesses whose nosological position is unclear. The article describes the origins and development of the PHC concept. The development of other diagnostic terms that are closely related to PHC is discussed, including paraphrenia, late-onset paraphrenia, and late-onset schizophrenia. The views of Gilbert Ballet and Gaëtan Gatian de Clérambault regarding PHC are also discussed. Attention is drawn to factors believed to cause PHC, including the phenomenon of psychological automatism. The position of PHC within psychiatric classifications is discussed. Arguments for and against the distinct diagnosis of PHC in psychiatry, particularly in contrast to schizophrenia, are presented.