<p>Real-life decisions typically involve multiple options, each with multiple attributes affecting value. In such complex situations, sequential shifts of attention to specific options and attributes are thought to guide the decision process. Using a task that allowed us to monitor attention during such multi-attribute decisions, we recorded decision-related signals in pre-supplementary motor area neurons from two male macaques. Attention influences activity in these neurons through two mechanisms. First, attention enhances the activity of neurons representing the currently sampled option, independent of its value, without fully suppressing the representation of other options. Second, attention up-regulates the gain of information integration towards the evolving value estimate for the attended option. In contrast, we found no evidence for a third suggested mechanism, in which only the attended option is represented. Instead, attention influences the ongoing parallel information accumulation and competition process by modulating the strength of the value information that drives this circuit.</p>