The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) has been used as a measure of cognitive decline in different cultures. The purpose of the study was to establish the validity and reliability of the Turkish version of IQCODE (IQCODE-T) and the ability of the questionnaire to distinguish between older adults with DSM-IV-TR dementia (n = 100) and healthy control participants (n = 60). In addition, the power of the IQCODE-T to distinguish between patients with depression and dementia was investigated. The Mini-Mental State Examination (MMSE) was performed on all participants and the IQCODE-T was administered to their informants. The IQCODE-T, which was not associated with age or education of the patients, significantly differentiated patients with dementia and controls. The IQCODE-T also correctly classified 73% of depressed patients as "non-demented". Because it is easy to administer, not associated with age/education and yields fewer false-positive results than the MMSE in depression, the IQCODE-T can be used in the detection of dementia.