Depression in dementia is known to deteriorate patients' cognitive function and Quality of Life and to increase the burden of care. Although detecting depression in dementia is crucial, there is no gold standard for its screening and diagnosis. We examined the psychometric properties of 3 different scales in detecting depression in dementia. Results will be useful as community services for dementia in the country are developing and the need for reliable detection of depression in dementia patients is urgent. Our sample consisted of 136 Greek dementia patients who consulted a memory clinic. For the diagnosis of depression, DSM-IV criteria for major depression and 3 different depression measures were used: a self-assessment scale (Geriatric Depression Scale; GDS), a caregiver assessment scale (Neuropsychiatric Inventory-Depression; NPI-D) and a clinician rated scale (Cornell Scale for Depression in Dementia; CSDD). For the evaluation of the screening performance of the three depression scales receiver operating characteristic curve (ROC) analysis was applied. The DSMIV criteria served as the gold standard method for the diagnosis of major depression. CSDD showed the best psychometric properties for the diagnosis of depression in dementia. The ROC curve analysis revealed that among the three measures, the CSDD had the wider AUC (0.919), second in the width of the AUC was the GDS (0.871), and last was the NPI-D (0.812). The prevalence of depression ranged from 18.4% according to DSM-IV criteria to 42.6% using the NPI-D. Using the GDS (cut off point: 7/8) and the CSDD (cut off point: 6/7), depression was present in 26.9% and 33.1% of the patients, respectively. Correlations between scales used were significant (r from 0.432 to 0.660; p<0.001). Caregivers tend to report more depressive symptoms in dementia compared to patients' and clinicians' ratings. CSDD should be used in specialized centers, but GDS may be an alternative in patients able to complete the assessment. The need to establish valid criteria for the diagnosis of depression in dementia is urgent.