A short period of post-encoding waking rest can enhance subsequent memory performance relative to a distractor task. This effect has been interpreted as evidence in favor of an opportunistic consolidation hypothesis (Mednick et al., 2011). According to this theoretical account, diversion retroactive interference (RI) induced by a distractor task inhibits episodic memory consolidation, whereas minimizing diversion RI through waking rest provides ideal conditions for such consolidation processes to occur. However, memory-enhancing effects of waking rest might also be interpreted in terms of similarity RI. This form of RI is assumed to depend on similarities between original and interpolated materials, and to affect memory at the level of retrieval. Therefore, any observable effect of post-encoding waking rest might be the result of some latent combination of both diversion and similarity RI (Dewar et al., 2007). In two conceptual replications of an experiment reported by Martini et al. (2020), we used a multinomial processing tree (MPT) modeling approach to disentangle storage and retrieval contributions to memory performances following waking rest versus a distractor task. After studying an Icelandic vocabulary list, participants spent the 8-min retention interval either wakefully resting, using Instagram on their own smartphones, or studying a Norwegian vocabulary list. Finally, participants were asked to retrieve the Icelandic vocabulary in a cued recall and a recognition test. Our results suggest a role for both diversion and similarity RI in the waking rest effect. Thus, future research will profit from a more careful consideration of both influences on forgetting in episodic memory.