BACKGROUND: Patients with Parkinson disease (PD) have deficits in the neurotransmitter systems important for the normal allocation of attention. We sought to examine how the presence of PD influences the spatial allocation of reactive (bottom-up) and volitional (top-down) attention. METHODS: To assess the spatial allocation of attention, we used the line bisection task. When assessing "bottom-up" attention, lateral blinking lights were or were not present during the time the PD and normal subjects were attempting to perform line bisections. In the top-down condition, these subjects were asked to name the color of the laterally presented light before bisecting lines. RESULTS: In the bottom-up condition, when compared with control subjects, the participants with PD were not abnormally distracted, but in the top-down condition, imperative stimuli on the right side of the line seemed to influence the PD subjects' allocation of attention. CONCLUSIONS: The results suggest that when voluntarily allocating attention rightward, PD patients have difficulty disengaging and/or reallocating their attention. This disengagement deficit might be related to the frontal-executive dysfunction associated with PD. © 2008 by Lippincott Williams & Wilkins.