Often patients and their families see Parkinson’s disease and dementia as cause and effect, believing that Parkinson’s disease will definitely develop into dementia later. In fact, this is a misconception. The two are different common geriatric diseases, and Parkinson’s disease is not dementia, nor will it necessarily be combined with dementia. Parkinson’s disease combined with dementia is mainly seen in two conditions, Parkinson’s disease dementia (PDD) and dementia with Lewy bodies (DLB), both of which are different from Alzheimer’s disease (AD), which is the most common disease with memory loss as the main manifestation. . Patients with Parkinson’s disease combined with dementia can have a significant impact on quality of life and significantly increase the burden on families, so we place more emphasis on early detection and intervention. When a person with Parkinson’s disease is found to have difficulty completing routine tasks, especially if the tasks require multiple steps and are in a certain order (e.g., cooking, organizing laundry) and confusion occurs (indicating impaired executive function), or if the person repeatedly reports seeing things, people, or animals that are not there (visual hallucinations), the presence of cognitive problems should be considered and prompt medical attention is needed. If a family member notices some abnormal behavior or decreased ability to live with Parkinson’s, the first step is to review the appropriateness of the medications being taken. Some medications may cause cognitive decline, such as Benzedrine, which improves tremor. Therefore, we do not recommend this medication for people over 70 years old. Some medications may cause hallucinations, such as agonists (pramipexole or piribedil), benzhexol, and amantadine, and it is recommended that these medications be discontinued and seen immediately if hallucinations occur. In case of Parkinson’s combined with dementia, anti-Parkinsonian medications can be added to improve cognitive status and clozapine to improve hallucinations or psychotic symptoms. Along with medication, the care and support of family members is even more important for patients.