Cognitive impairment in Parkinson's disease (PD) has been determined to be due to the interruption of frontal-subcortical neural circuits. To evaluate which kind of frontal-subcortical dysfunction may be present and the relationship of this dysfunction with P300 in PD patients, non-demented PD patients and controls were rendered for comprehensive Frontal Test Battery and P300 assessments. PD patients manifested significantly with frontal dysfunction and revealed a good correlation between P300 and executive dysfunction. We conclude that PD patients may manifest with cognitive impairment related to frontal dysfunction, and P300 may be an indicator reflecting the evolution of dysexecutive syndrome.