Psychotic symptoms, including delusions and hallucinations, frequently complicate the course of Alzheimer's disease (AD), dementia with Lewy bodies (DLB), Parkinson's disease dementia (PDD), and frontotemporal dementia (FTD). Their presence accelerates decline, worsens outcomes, and complicates management. Cognitive screening in such patients is essential yet challenging due to attentional fluctuation, impaired insight, and diagnostic overlap. Addenbrooke's Cognitive Examination III (ACE-III) is a multidomain tool with higher sensitivity than the MMSE. Evidence indicates that ACE-III captures disorder-specific cognitive-psychotic profiles: memory impairment in AD with delusions of theft, visuospatial and attentional deficits in DLB with hallucinations, or executive dysfunction in FTD with paranoid ideation. Mini-ACE (M-ACE), a shorter derivative, is useful in acute psychiatric or advanced dementia settings. This review synthesizes evidence on ACE-III and M-ACE in psychosis-related neurodegeneration, highlights their role in differentiating from primary psychiatric psychoses, and identifies knowledge gaps, particularly in atypical AD variants, mixed dementia, and autosomal dominant AD. ACE-III emerges as a practical and informative tool, but psychosis-specific normative data and longitudinal studies are needed.