Progressive supranuclear palsy (PSP) and cortocobasal degeneration (CBD) are often clinically confused with each other because they share a rapid disease progression, parkinsonism that responds poorly or transiently to levodopa therapy, and associated signs (e.g., ocular abnormalities, pyramidal signs and cognitive involvement). To improve the accuracy in diagnosing these disorders, this study examined the clinical features of 51 patients pathologically diagnosed with PSP and CBD. Logistic regression analysis identified two sets of predictors (models) for CBD patients, one consisting of asymmetric parkinsonism, cognitive disturbances at onset and instability and falls at first clinic visit, and the other one of asymmetric parkinsonism, cognitive disturbances at symptom onset and speech disturbances. While PSP patients often had severe postural instability at onset, symmetric parkinsonism, vertical supranuclear gaze palsy, speech and frontal lobe-type features, CBD patients presented with lateralized motor (e.g., parkinsonism, dystonia or myoclonus) and cognitive signs (e.g., ideomotor apraxia, aphasia or alien limb). On the other hand, CBD patients presenting with an alternate phenotype characterized by early severe frontal dementia and bilateral parkinsonism were generally misdiagnosed. PSP patients without vertical supranuclear gaze palsy were misdiagnosed. Recognizing the features which differentiate these disorders and the less obvious disease presentations as well as developing an increased index of suspicion will improve the diagnostic accuracy of these disorders.