the growing evidence of the possibility of fake or manipulated performance in forensic neuropsychological assessment context, including cases involving older adults (e.g., disability determinations or early retirement requests), requires assessing specifically insufficient effort or malingering. the rey 15-item memory test (15-imt) is one of the most commonly used instruments in this context. it must be acknowledging that the ceiling effect behind the development of insufficient effort or malingering tests may not result in the same way in people with mental illness or dementia, groups of older adults with certain medical conditions, such as neurodegenerative disorders, who are also usually excluded from validation studies. therefore, we will analyze the performance of different groups of older adults in this test (healthy, with cognitive problems and with depression), in comparison with a group of young adults (control), with the aim of examine its validity and the value of different cut off points. the results indicate excellent specificity of the cut off <9 in immediate recall and <20 in the combined result of the recognition in the group of young adults. however, the same cut off points are not applicable in samples of older adults, suggesting that they are not adequate for analyzing the performance of people with real deficits or even elderly people without cognitive problems.