There is growing evidence that cognitive bias modification procedures targeting attention (CBM-A) can alter anxiety reactivity in the laboratory, and also can yield therapeutic benefits for clinically anxious patients. These promising findings underscore the need for investigators to delineate the conditions under which CBM-A procedures are effective. In the present research we conducted two studies to empirically determine whether CBM-A continues to be effective when participants are informed of the training contingency and instructed to actively practice the target pattern of attentional selectivity. These studies were designed to address two key questions relating to this issue. First, if participants are informed of the training contingency and instructed to practice the target pattern of attentional selectivity, then will the CBM-A manipulation still effectively modify attentional response to negative information? Second, if it does still modify attentional response to negative information under these conditions, then will this change in attentional selectivity still serve to alter anxiety responses to a stressful experience? The results indicate that when participants are informed of the training contingency and instructed to practice the target pattern of attentional selectivity, then the CBM-A manipulation continues to exert an impact on attentional selectivity, but this modification of attentional bias no longer affects anxiety reactivity to a subsequent stressor. We discuss both the theoretical and practical implications of these findings.