Even though there are several reports on P300 changes as a measure of cognitive disturbances in Parkinson’s disease (PD), there have been relatively few number of studies investigating P300 topography. In order to evaluate cognitive functioning by means of the changes in P300 mapping, we prospectively studied 16 PD patients, and 15 healthy controls. P300 mapping was elicited by standard auditory oddball paradigm and recorded from the 10-20 system electrod localizations with linked-ears reference. Changes in latency, amplitude and topography of P300 activity were correlated with the results of MMSE (Mini Mental State Examination). Among our PD cases only 2 were demented, and these cases had prominent increase in P300 latency. In nondemented PD patients, P300 latency was not significantly longer than controls. Although P300 activity was most prominent in the parieto-central region topographically, it was more anteriorly localized only in 2 of the PD patients, one of whom was demented. We conclude that P300 latency is useful in detecting cognitive dysfunction in PD and P300 topography may add only a small amount of sensitivity to conventional P300 evaluation