This study combined an individual differences approach to interrogative suggestibility (IS) with ERP recordings to examine two alternative hypotheses regarding the source of individual differences in IS: (1) differences in attention to task-relevant vis-à-vis task-irrelevant stimuli, and (2) differences in one or more memory processes, indexed by ERP old/new effects. Sixty-five female participants underwent an ERP recording during the 50 min interval between immediate and delayed recall of a short story. ERPs elicited by pictures that either related to the story (“old”), or did not relate to the story (“new”), were recorded using a three-stimulus visual oddball paradigm. ERP old/new effects were examined at selected scalp regions of interest at three post-stimulus intervals: early (250-350 ms), middle (350-700 ms), and late (700-1100 ms). In addition, attention-related ERP components (N1, P2, N2, and P3) evoked by story-relevant pictures, story-irrelevant pictures, and irrelevant distractors were measured from midline electrodes. Late (700-1100 ms) frontal ERP old/new differences reflected individual differences in IS, while early (250-350 ms) and middle latency (350-700 ms) ERP old/new differences distinguished good from poor performers in memory and oddball tasks, respectively. Differences in IS were not reflected in ERP indices of attention. Results supported an account of IS as reflecting individual differences in postretrieval memory processes.