Research summary: Exploiting opportunities is critical to a firm's competitive advantage. Not surprisingly, there has been considerable interest in the processes by which top managers allocate attention to potential opportunities. Although such investigations have largely focused on top‐down processes for allocating attention to the environment, some studies have explored bottom‐up processes. In this article, we consider both top‐down and bottom‐up processing to develop a model by which top managers form opportunity beliefs for strategic action depending on the allocation of transient and sustained attention. Specifically, this attentional model provides insights into how a top manager's attention is allocated to identify potential opportunities from environmental change and explores how different modes of attentional engagement impact the likelihood of forming beliefs about radical and incremental opportunities requiring strategic action. Managerial summary: Managers are interested in noticing and exploiting opportunities because the exploitation of an opportunity represents an important strategic action. Noticing and exploiting opportunities depends on how and where top managers allocate their attention. Managers can focus attention based on their knowledge and experience or as a result of something in the environment capturing their attention. In this paper, we consider both knowledge‐driven and environment‐driven processes for allocating attention to form opportunity beliefs. This opportunity belief arises from a two stage process. The first stage explains how a top manager identifies environmental changes as potential opportunities. The second stage explains how the top manager forms a belief that these identified environmental changes represent a radical or incremental opportunity worthy of exploitation. Copyright © 2016 John Wiley & Sons, Ltd.