Mindfulness-based cognitive therapy (MBCT) effectively prevents relapse/recurrence in major depression. The ability to deploy and maintain attention on a particular focus is considered as a prerequisite for 'mindful', 'metacognitive' awareness, and hence crucial for therapy success. Accordingly, sustained concentration is the skill most extensively taught in MBCT. The goal of the present study was to test whether this ability increases after MBCT, as assumed. The late component of the contingent negative variation (CNV), an event-related brain potential (ERP), known to reflect the allocation of attentional resources, was used as the measure of concentration ability. In the main phase of the study, 91 recurrently depressed patients in remission were randomly assigned to eight-week treatment by either MBCT or waiting (WAIT for delayed MBCT). The CNV response to an auditory test stimulus was measured pre- and post-treatment in a 'mindfulness task', in which patients were instructed to focus on their breath, as taught in MBCT. The late CNV (LCNV) was increased only after MBCT (and not after WAIT). This result reflects patients' improved ability to shift their attention toward current moment experience and away from potentially depressogenic thinking or rumination during mild dysphoric states-a known risk factor for depressive relapse/recurrence.