Patients with Parkinson's disease (PD) present motor symptoms (bradykinesia, rigidity, resting tremors) and often non motor symptoms, like cognitive impairments and neuropsychiatric disorders. This reviews takes in exam cognitive impairments of PD patients, primarily of executive functions, memory and visuospatial functions, but other cognitive functions may result impaired, as secondary consequence of the primary executive dysfunction. Then not yet well-studied aspects of cognition in PD are presented, tracing directions for future researches: 1) the concept of Mild Cognitive Impairment and the early identification of cognitive predictors of dementia 2) the concept of Cognitive Reserve 3) the relation between cognition and dopaminergic therapy. This paper may be an operative tool for neuropsychologists working in clinical and experimental settings dealing with cognitive aspects of Parkinson's disease.