By using a cube-copying task, visuospatial impairment in patients with Parkinson's disease was identified and studied in relation to the performance IQ, neuropsychological symptoms, and activities of daily living. In addition, a quantitative assessment of the performance IQ was also attempted by establishing a scoring guideline for the copying task. The results indicated that the subjects' performances in the copying task correlated to motor function, visuospatial impairment, and the results from the mobility and social cognition subtests of the Functional Independence Measure. The quantitative evaluation of the results from the copying task also showed a high correlation to the patients' constructional ability, assessed by the Block design and the Object assembly tasks from the Wechsler Adult Intelligence Scale-Revised. This study demonstrated that visuospatial deficits in Parkinson's disease patients were associated with impairments in both activities of daily living and motor function. In addition, quantitative assessment of the copying task suggested that this test may be predictive of the nonverbal IQ. Therefore, we concluded that the copying task is a useful tool for the assessment of visuospatial impairment in patients with Parkinson's disease; these deficits may be associated with an increased risk of motor dysfunction such as difficulties in the activities of daily living.