Clinical psychologists describe decentering as the mental operation in which a subject ‘moves out’ of immersion in a mental state. Such decentering is philosophically puzzling. It involves that a subject attends to her mental state to distance herself from it. That is, she attends to the state to make it less determining of her processing. This paper provides a philosophical explanation of the nature of decentering. It analyses decentering as a complex mental operation composed of two sub-operations: introspection and detachment. Drawing on this analysis, the paper argues that decentering involves certain dynamics of attention and attention control that pose an important challenge to a selection for action theory of attention. This challenge concerns adequately describing the workings of detachment in decentering. The paper discusses how a selection for action theory might reply, yet it argues that all the available replies involve unattractive aspects. The paper closes with broader perspectives, suggesting that decentering might also pose a puzzle for other theories of attention.