Mindfulness meditation can reduce the effects of mind-wandering, but how? Meditation may reduce mind-wandering directly by reducing distracting thoughts or improving sustained attention. Alternatively, meditation may not reduce mind-wandering itself, but enhance the ability to detect and correct mind-wandering. Disentangling these mechanisms is difficult because subjective reports of mind-wandering depend on both factors, but in opposing ways. For example, meditators often report increased awareness of distracting thoughts in the early stages of practice, sometimes creating the frustrating impression that meditation increased their mind-wandering. However, instead, this impression is often attributed to increased awareness of normally-occurring mental activity. By contrast, advanced meditators often report a subjective decrease in distracting thoughts, but this change is often attributed to a genuine decrease in mind-wandering. Despite their intuitive appeal, these accounts currently cannot be corroborated because current methods cannot differentiate between changes in awareness of mind-wandering and changes in susceptibility to mind-wandering. Therefore, our goal is to develop a neurophysiological marker of attentional state to help differentiate between these mechanisms. By comparing subjective reports of mind-wandering with neural indicators of attentional state, we hope to separately index changes in meditators’ susceptibility to mind-wandering and their ability to detect attentional lapses as their practice develops.