Attentive tracking shows independent attentional limits for the left and right visual hemifields (Alvarez & Cavanagh, 2005), whereas visual search does not (Luck et al., 1989). We test whether location-based filtering is the critical process that operates independently in the two hemifields: it is present in tracking (attend to a subset of items, suppress the others) but not in standard visual search (all items are potential targets). Method: We devised a subset visual search where16 black placeholders were presented and 2 to 10 of them were then cued, with either bilateral (half in each hemifield) or unilateral cues (all in one hemifield). After one second, the placeholders became 16 letters (one T and 15 Ls). The T always appeared within the cued subset and observers were instructed to search only in the subset and report the orientation of the T. In the standard condition 2-10 letters (the target T among Ls) were presented either bilaterally or unilaterally. Results: Consistent with previous research, there was no difference in search slope between the bilateral and unilateral displays in the standard task (t(13)=1.05, p=.31). However, in the subset task, search slopes were 1.35 times steeper for unilateral displays relative to bilateral displays (t(13)=2.83, p<.05). Conclusion: There is some hemifield independence in a visual search task when the task requires observers to attend to a subset of the items while suppressing the others. These results suggest that hemifield independence is a property of location-based, attentional filtering.