Objective: The objective of this systematic descriptive review was to make a summary and a qualitative analysis on the efficiency of the Confusion Assessment Method (CAM) as a diagnostic tool for acute confusional syndrome (ACS). Methodology: We carried out a search in PubMed, PsychoInfo, MEDES, SciELO, Cochrane, Medline, Embase, Central, CUIDEN, Google Scholar, Academic Search, magazines, books and we made other manual searches of citations in other means of scientific disclosure. We used the MeSH descriptors: delirium, reliability, sensitivity and specificity, and the free term: confusion assessment method, which generated 756 potentially eligible articles, from 2009 to 2014.Results: 0.66% diagnostic studies were found, from which two were about validation and cultural adaptation to Thai, one to German, one about validation in palliative care patients and the last found was a comparative cohort evaluation of the efficiency of the CAM scale compared to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and International Classification of Diseases (ICD-10). Conclusion: CAM scale is a valid, reliable and safe diagnostic tool with high performance, when it is handled by trained professionals for clinical diagnosis of ACS. It is necessary to develop more research into routine practices of professional nursing.