Persistent schizophrenias and delusional disorders are classified as primary psychiatric pathologies amongst the elderly. It is crucial to distinguish them from secondary psychotic disorders associated with physical illnesses, such as acute confusion and psychotic symptoms caused by dementia or other somatic pathologies. Employing the concept of a primary psychiatric disorder occurring in an elderly patient is not simple, and each term used to define the concept refers back to an array of various criteria in clinical, psychological, biological, neurological, and cognitive fields. What about very late-onset schizophrenia, occurring after the age of 60 years, for instance? Is this a primary psychiatric illness occurring very late or a secondary pathology caused by brain disease, particularly a degenerative one? Studies reveal controversial results and it is still being debated as to whether the disease has neurodevelopmental or neurodegenerative causes. Due to the variable symptoms and psychiatric, somatic, and cognitive comorbidities associated with psychosis in elderly patients, patient healthcare must not be limited to prescribing an antipsychotic. Once it has been determined whether the psychosis is secondary or primary (old-agerelated schizophrenia, late-onset or very late-onset schizophrenia, or late-onset delusional disorder), an aetiological or symptomatic treatment must follow, including a psychotherapeutic approach, close surveillance of the drug treatment and its potential side-effects, rehabilitation steps through community-based care, and psychoeducational support for the family and other professionals in charge of the patient. Our article's aim has been restricted to summarising our understanding regarding late-onset schizophrenias and delusional disorders amongst the elderly.