Detachment (self-focused) and positive reinterpretation (situation-focused) are two important forms of cognitive reappraisal during emotion regulation. Previous research shows situation-focused reappraisal to be more effective than self-focused reappraisal for intentional emotion regulation. How the two differ in emotional consequences as components of automatic emotion regulation is however unclear. In the current study, event-related potentials were recorded to clarify this problem, while participants passively viewed disgusting or neutral scenes or formed implementation intentions based on self-focused or situation-focused reappraisal. Behavioural results showed fewer negative emotions during self-focused reappraisal than during either situation-focused reappraisal or free viewing (which had similar emotion ratings). In addition, self-reported cognitive cost was not enhanced during the two forms of reappraisal compared to passive viewing. Late positive potential (LPP) amplitudes for disgusting stimuli were larger than those elicited for neutral stimuli, at both frontal and posterior-parietal regions. This amplitude enhancement effect, irrespective of whether frontal or parietal LPP were involved, was found to be weaker during self-focused reappraisal than when participants were engaged in situation-focused reappraisal or passive viewing. The latter two conditions showed similar amplitude enhancement. These findings suggest that automatic self-focused reappraisal by implementation intention produces more favourable emotion regulation than situation-focused reappraisal, without enhancing cognitive cost.