The development of studies of aging patients with schizophrenia results from their increasing life expectancy in accordance with that of the general population, but remains far below that one. Studies devoted to cognitive deficits in these patients globally show various complex cognitive deficits, which usually remain stable in their evolution. However, some patients develop a severe cognitive decline after 65 years, following a long institutionalization. Complex cognitive functions particularly deserve to be systematically explored in patients presenting with cognitive complaints and/or communication difficulties. As an example, we present the case report of a patient showing a theory of mind deficit.