Summary:The frequency of depression is increased in Parkinson's disease. Similar cognitive changes were reported in depressed patients and in parkinsonian patients. We compared memory, language generation, set shifting, and visual spatial abilities in parkinsonian patients with depression, parkinsonian patients without depression, depressed patients and normal elderly. Severity of depression and of motor impairment were comparable in the appropriate comparison groups.Parkinsonian patients with depression were significantly worse than the others on delayed recall of objects, in ability to use cues to establish a consistent recall strategy, and in shifting cognitive set. Results suggest that depressed parkinsonian patients have more severe frontal cognitive dysfunction than nondepressed parkinsonian and depressed patients. The impaired performance of the parkinsonian patients with depression may not result from depression per se, but may result from involvement of additional neural systems.