The present chapter aims to analyze the contribution and relevance of neurocognitive assessment in diagnosis and treatment design in schizophrenic spectrum disorders (SSD). The observation of cognitive affections was included in the first descriptions associated with schizophrenia. However, its importance has been recently recognized: in the face of neuroscience advances, its value for the prediction of the evolutionary course of the disease has been repeatedly highlighted.After a brief analysis of the consequences that the current psychiatric nosography has raised for the clinic and the research, a review of the most frequent cognitive alterations in SSD and the corresponding strategies of investigation are proposed, considering its linkages with the behavioral and positive symptoms, personality variables, and social difficulties. The influence of schizophrenia-associated disorders such as substance abuse, anxiety, and depression was also included. Finally, some aspects about the neurocognitive rehabilitation programs are presented. We believe that this chapter could help to orientate new research projects. But also, to encourage the clinical application of functional neuro-evaluation tasks and neuro-rehabilitation protocols.These measures could promote the constitution of therapeutic offers that, together with pharmacological treatment and psychotherapy, would give the patient an active participation in the improvement of their quality of life.