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The present study aims to be the first to validate the Tuokko version of the Clock Drawing Test (CDT) and estimate its cutoff score after its translation into the Greek language and administration in the Greek population. One hundred and thirty-two individuals participated in this study [60 with Good Cognitive Health (GCH), 24 with Parkinson's Disease (PD), 24 with Parkinson's Disease Dementia (PDD) and 24 with Alzheimer's Disease (AD)]. The CDT was administered to all participants. Additionally, the cognitive and mental status of the sample were estimated through the use of the Mini Mental State Examination (MMSE), Abbreviated Mental Test Score (AMTS), Arizona Battery for Communication Disorders of Dementia (ABCD), Instrumental Activities of Daily Living (IADL), the Neuropsychiatric Inventory (H-NPI) and the Geriatric Depression Scale −15 (GDS-15). Statistically significant differences were found between all groups on the CDT, with AD patients having lower scores than all subgroups in the study. The CDT showed a high internal consistency (Cronbach's alpha = 0.832). The ROC analysis provided a cutoff point equal to 4.00 (AUC: 0.821, p < 0.001) between the Cognitively Unimpaired Group (CUG: GCH and PD group) and the Cognitively Impaired Group (CIG: PPD and AD patients), 5.00 (AUC: 0.845, p < 0.001) between the GCH group and the PDD group, and 4.00 (AUC: 0.780, p < 0.001) between the GCH group and the AD group. Finally, the cutoff point between the PD group and the PDD group was 4.00 (AUC: 0.896, p < 0.005), and 3.00 (AUC: 0.899, p < 0.001) between the PD group and the AD group. Significant positive Pearson's correlations were observed between CDT and MMSE (r = 0.808, p < 0.001), CDT and AMTS (r = 0.688, p < 0.001), CDT and ABCD (r = 0.770, p < 0.001), CDT and the ABCD Visuospatial Construction subdomain (r = 0.880, p < 0.001); while a negative correlation was found between CDT and IADL (r = −0.627, p < 0.001) between the CUG and the CIG groups. Given the results obtained, the CDT appears to be a clinically valid screening instrument for the assessment of visuospatial abilities, with high reliability in Greek populations with cognitive impairment. [ABSTRACT FROM AUTHOR]