Memories of internally generated events (e.g., thoughts, dreams, imaginations) are encoded, stored, and retrieved similarly to memories of real events. In the present set of experiments, functional magnetic resonance imaging (fMRI) was used to examine whether brain regions known to support episodic memory processes are differentially activated during retrieval of memories that were acquired through perception versus imagination. In three experiments, subjects perceived and imagined events in response to a cue word, and then after a delay made memory judgments about previously perceived, imagined, and new events. Experiment 1 demonstrated that regions of the left lateral posterior parietal cortex (LPPC) were more active during retrieval of perceived compared to imagined events, regardless of memory accuracy. Experiments 2 and 3 replicated this effect, and also provided evidence that observed source-based differences in activity could not be attributed to differences in the perceptual vividness of memories from perception versus imagination. And Experiment 4 demonstrated that source-based differences in activity occurred regardless of differences in response bias. Each of these experiments also revealed that successful retrieval effects in LPPC were source-specific. Correct recognition of old events was associated with a greater LPPC response than correct rejection of new events for items that were perceived at encoding, but not for those that were imagined. Combined, these studies suggest that the LPPC plays a preferential role in the retrieval of memories of perceived compared to imagined events, and this does not appear to be due to discernable differences in task demands or behavioral performance. Implications of these findings for both theories of functional contributions of LPPC to recognition memory as well as the neural mechanisms underlying our ability to discriminate the perceived versus imagined source of memories are discussed.