Z. V. Segal et al. (2006) demonstrated that depressed patients treated to remission through either antidepressant medication (ADM) or cognitive-behavioral therapy (CBT), but who evidenced mood-linked increases in dysfunctional thinking, showed elevated rates of relapse over 18 months. The current study sought to evaluate whether treatment response was associated with gains in decentering-the ability to observe one's thoughts and feelings as temporary, objective events in the mind-and whether these gains moderated the relationship between mood-linked cognitive reactivity and relapse of major depression. Findings revealed that CBT responders exhibited significantly greater gains in decentering compared with ADM responders. In addition, high post acute treatment levels of decentering and low cognitive reactivity were associated with the lowest rates of relapse in the 18-month follow-up period.