Almost 40years ago, Boller et al. published a set of papers documenting the cognitive and neuropathological changes in some patients with Parkinson's disease (PD), which apparently contradicted the classic notion enunciated by Parkinson himself that “the senses and intellect are uninjured” in these patients. However, Charcot and Vulpian and, more recently, M. Neuman, E.C. Alvord and M. Victor had earlier noted cognitive and/or neuropathological impairment in PD patients. These findings sparked a debate to establish whether cognitive deficits were part of the disorder or whether they could be explained by other mechanisms, such as depression, pharmacological treatments or even the coincidental development of age-related pathologies such as Alzheimer's disease. At this time, the presence of cognitive impairment has been clearly established through formal neuropsychological evaluations of larger sample populations, and there is agreement that a wide range of cognitive dysfunction arises in PD. Such changes can be distinguished from other dementia syndromes, and PD is now considered a subcortical dementia characterized by changes in processing speed, attention and working memory especially in the visuospatial domain, in addition to the involvement of language and episodic memory, and disturbances in mood and behavior. In conclusion, it is now established that, in PD, in addition to the motor symptoms (tremor, bradykinesia, rigidity, postural instability), patients often manifest a heterogeneous range of cognitive impairment and neuropsychiatric symptoms, which impact their daily lives and require a specific therapeutic approach.