Cognitive dysfunctions are critical determinants of the quality of life and functionality in schizophrenia. Whether the cognitive deficits present at an early stage, are static or change across one's lifespan is still under debate. This study aims to investigate the long-term (3years) course of cognitive deficits in a large and representative cohort of first episode schizophrenia spectrum patients (N=155),and evaluate their influence on disability. In addition, a healthy control sample (N=43) was also studied for comparison. This study evaluates the performance of patients and controls in a battery of cognitive assessments using baseline, 1-year and 3-year follow-up designs. The results show that, although cognitively outperformed by the controls at any time, the cognitive performance of the patients improved similar to the controls in all cognitive functions except verbal and visual memory. Even though the course of cognitive performance across the sample as a whole was stable, the subgroup of patients who experienced a cognitive decline had worse functionality and lesser amelioration of negative symptoms. Overall, there is no significant deterioration in the cognitive function in a group of first episode schizophrenia spectrum disorder patients, with the possible exception of tasks that were associated with episodic memory. However, patients whose cognitive performance demonstrated a declining trend may present with a poorer progression in terms of clinical and disability variables.