Perspective and classification of the Parkinson Disease (PD) has changed significantly over the last decade: PD is now defined as pathognomonic Lewy bodies in nigral dopaminergic cells. Pathological changes actually occur in the brain stem of PD patients several years before the first motor symptoms appear and these patients may show subtle cognitive changes very early during the course of the disease, eventually leading to dementia in almost all cases. Several clinical diagnostic criteria exist for dementia associated with PD (PDD); moreover, clinical profiles and brain changes are similar to dementia with Lewy bodies (DLB). The cognitive profiles of PDD and DLB have been characterized as including visuospatial, attentional and executive impairment with relatively less impairment of memory. These patients suffer from fluctuations in consciousness and cognition and neuropsychiatric symptoms such as REM sleep disorders, mood disorders (depression, anxiety), and visual hallucinations. Such a diverse variety of cognitive symptoms emphasizes the importance of different symptomatic treatment targets and suggests the use of a variety of targeted agents: acetyl cholinesterase inhibitors, in particular, rivastigmine, and SSRIs and SNRIs for depression. However, antipsychotic drugs should be used with caution because of their adverse effects. While keeping the symptoms at bay, the next key goal for therapy will be to alter the underlying disease process itself.