Originally named in the 1970s by Dr. Stanley Fahn, Parkinson-plus or atypical Parkinsonism refers to a group of neurodegenerative disorders that are distinct from idiopathic Parkinson's disease (PD) but share its central features of bradykinesia, rigidity, tremor, and gait disturbances . The “plus” or “atypical” descriptor indicates the presence of features not typical in patients with idiopathic PD, such as early and severe autonomic disturbances exhibited by patients with multiple system atrophy (MSA), vertical supranuclear palsy by those with progressive supranuclear palsy (PSP), and early postural instability and falls by both of them. The atypical Parkinsonian disorders account for approximately 10-20% of all Parkinsonisms and are characterized by atrophy to multiple cortical and subcortical networks. Cognitive and behavioral disturbances are often present in the early stages of the atypical Parkinsonian disorders. In this chapter, three of the most common atypical Parkinsonian disorders (MSA, PSP, and corticobasal degeneration [CBD]) are reviewed, with particular emphasis given to the cognitive and behavioral features of the disorders. A brief history of the atypical Parkinsonian syndromes will also be included along with incidence rates, affected brain regions, presenting complaints, and clinical features that assist with differential diagnosis, both from PD and from each other.