Research with normal participants has demonstrated that mechanisms of selective attention can simultaneously gain access to internal representations of spatial information defined with respect to both location- and object-based frames of reference. The present study demonstrates that patients with unilateral spatial neglect following a right-hemisphere lesion are poorer at detecting information on the contralateral left side in both location- and object-based spatial coordinates simultaneously. Moreover, the extent of the neglect is modulated by the probability of a target's appearing in either reference frame; as the probability of sampling a target in a particular frame of reference increases, so does the severity of neglect in the frame. These findings suggest that attention can be flexibly and strategically assigned to a reference frame depending on the contingencies of the task.