<p>Mind-wandering and daydreaming are often treated as synonymous in the literature, yet it remains unclear whether they represent the same cognitive phenomenon in everyday experience. Although mind-wandering and daydreaming are used interchangeably, there are reasons to argue that they relate to two different cognitive phenomena. This study aimed to investigate the differences and similarities between mind-wandering and daydreaming. Using an experience sampling method, participants reported episodes of mind-wandering and daydreaming ten times daily at fixed intervals over seven days. We compared these episodes in terms of phenomenological characteristics and their relative frequency of occurrence. The observed differences were consistent across participant-level analyses and episode-level mixed-effects models, supporting the distinction between mind-wandering and daydreaming as related but separable cognitive phenomena.</p><p>The stage 1 protocol for this Registered Report was accepted in principle on 22/01/25. The protocol, as accepted by the journal, can be found at: <a href="https://doi.org/10.6084/m9.figshare.28945814">https://doi.org/10.6084/m9.figshare.28945814</a></p>