Cognitive Remediation Therapy (CRT) is a novel rehabilitation approach designed to improve neurocognitive abilities such as attention, memory and executive functioning. The aim of the present study is to evaluate the effect of CRT on neurocognition, and secondarily on symptomatology and psychosocial functioning. Cognitive Behavioural Therapy (CBT) was used as a control condition because it aims to improve emotional problems and positive symptoms, focusing on modification of maladaptive beliefs and schemas, but neurocognition is not targeted. A total of 40 chronic patients with DSM-IV schizophrenia disorder were randomly assigned for 4 months to one of two treatment groups: CRT or CBT. Repeated assessments were conducted before and after the treatments and at the end of a follow-up period of 6 months. Additionally, a method to establish reliable change was calculated from a separate sample of 20 schizophrenic patients who were under standard medication without any kind of psychological treatment. Results showed that CRT produced an overall improvement on neurocognition (Mean effect size=0.5), particularly in verbal and nonverbal memory, and executive function. CBT showed the expected treatment effect on general psychopathology (anxiety and depression) but produced only a slight non-specific improvement in neurocognition (Working Memory). Furthermore, patients receiving CRT showed improvement in social functioning, demonstrating that cognitive improvements are clinically meaningful. These gains were still present at the 6 month follow-up.