Background and Objectives: Prefrontal cortex (PFC) dysfunctions leading to cognitive deficits refer to a core feature of schizophrenia spectrum disorders (SSD). This exploratory study compares the effect of SSD on two stages of maturation of PFC. Methods: Using functional magnetic resonance imaging (fMRI), we measured the brain correlates related to a verbal fluency task (a hallmark executive function test) in 12 patients with SSD: 6 adolescents (SSD-ado) and 6 adults (SSD-adu). Results: SSD-ado showed greater activation in insula, thalamus and hIP1 whereas SSD-adu recruited more intensively precentral gyms and temporal pole to resolve the task. Thus, adolescents with SSD seem to adopt less frontal mediated strategic processes. In contrast. adults seem to be able to use PFC mediated strategy despite the well-known deleterious effect of SSD on the PFC. Conclusions: This first exploratory study revealed that adults and adolescents with SSD seemed not to use the same strategy to resolve a verbal fluency task. Thus, despite the illness, which is known to have a deleterious influence on PFC, adult patients seem to be able to recruit these resources to perform an executive function task. Further studies are needed in order to confirm and extend these new and preliminary results.