OBJECTIVE: The reliability and validity of the Cornell Scale for Depression in Dementia were investigated in a Turkish population over 60 years of age. METHOD: Forty-six male and 34 female demented elderly people classified as demented according to DSM-IV criteria were included in the study. The Structured Clinical Interview for DSM-IV Clinical Version (SCID-I) was completed for all subjects to establish the diagnosis of major depression. The Cornell Scale for Depression in Dementia (CSDD), Geriatric Depression Scale (GDS), Mini Mental State Examination (MMSE) and Global Deterioration Scale (GDS) were used. RESULTS: A high test-retest correlation level (r: 0.93) was obtained for the total scores of the scale. The scale also showed high internal consistency (a: 0.86). The validity analysis of the scale resulted in a significant difference (p<0.001) between the total scores of the group with dementia and depression and the group with dementia but without depression. Two items (9-19) showed a low correlation (r<.30) in the test-retest analysis. On the other hand, two items (6-19) had a low item-total score correlation (r<.30). CONCLUSIONS: The results indicated that the scale is reliable and valid for diagnosing depression in dementia in an elderly Turkish population. We expect that the Cornell Scale for Depression in Dementia will be a useful instrument in pharmacological investigations and in studies of the phenomenology and course of depressive symptoms in demented patients.