Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease, and it is characterised by tremor, bradykinesia, rigidity and postural instability. The most frequent cognitive disorder is executive dysfunction, although global deficits associated to late onset of the disease have also been reported.To describe and to compare cognitive performance in three groups with PD and one with Parkinsonism.A neurological and neuropsychological evaluation was carried out on 175 patients with idiopathic PD and Parkinsonism. The data analysis was performed by comparing the results of the tests carried out on the four groups: three with PD (age of onset: juvenile, adult and late) and one with Parkinsonism, while controlling for age, schooling and time of progression.In the juvenile PD group, alterations were observed in the number of intrusions in verbal memory; in the adult PD and late PD groups, there were alterations in time in continuous visual execution. These differences disappeared when the groups were compared to each other while also controlling for age. The Parkinsonism group obtained results that were lower than those of all the groups with PD for most of the cognitive and functional variables.Idiopathic PD would not be the cause of multiple cognitive impairment, but of a specific alteration, mainly involving the speed of processing and information recall. Age of onset would not be a decisive factor in the degree of impairment of cognitive functioning; important cognitive impairment was only present in the group with Parkinsonism.