BACKGROUND Chronic renal and liver diseases are associated with cognitive and intellectual impairment, which can be irreversible even after kidney or liver transplantation. OBJECTIVE We sought to investigate the presence of cognitive deficits in organ transplantation candidates. METHODS From May 2005 to March 2006, 35 organ transplantation candidates, of mean age 46.71 (+/- 13.01) years, 54.3% including females and 7.29 (+/- 4.22) years mean formal schooling. Of those, 27 (77%) were renal and 8 (23%), liver transplantation candidates. All subjects underwent a neuropsychological assessment battery designed to evaluate attention performance, executive functions, memory, language, visuaospatial, and intellectual skills. RESULTS We found impairments in attention performance (attention span [34.3%], sustained attention [76.5%], and divided attention [77.8%]), executive functions (category formation [58.3%], errors [61.5%], and perseverative errors [30.4%]), memory (working memory [57.1%], verbal [37.1%] and visual short-term memory [31.4%], verbal [25.7%] and visual long-term memory [51.4], verbal learning [42.9%], interference susceptibility [42.9%], and verbal recognition memory [20.6%]), language (comprehension [38.1%], and vocabulary [30.8%]), visuaospatial (45.8%), and intellectual skills (50.0%). CONCLUSIONS Neuropsychological (cognitive) deficits in transplant candidates are frequent, regardless of the kind of transplantation. The deficits involve several cognitive skills, such as attentional processes, executive functions, memory, language, visuaospatial, and intellectual skills. Therefore, we concluded that a pretransplant neuropsychological assessment is an important measure to detect impairments and to help understand how these difficulties can interfere with patient self-care before and after transplantation.