Body size may have a significant impact on arboreal locomotion, as small animals are more capable of navigating on smaller branches, acquire increased stability due to the lower position of the center of mass, and small substrates appear larger to them, compared to larger animals. To determine whether gaits are also affected by body size in relation to substrate size, we conducted a study on two sympatric arboreal glirid rodents of different size on simulated arboreal substrates. Our preliminary results showed that the smaller Muscardinus avellanarius used symmetrical walking gaits on the narrowest substrates (2 mm), moved significantly faster using asymmetrical bounding gaits with increased aerial phases on larger substrates, and regulated velocity via stride length. On the other hand, the larger Glis glis failed to move on 2 mm and 5 mm substrates, used asymmetrical gaits at lower velocities and decreased aerial phases on larger substrates, and regulated velocity mainly via stride frequency. We suggest that the observed differences in gait metrics may be related to body size and to the utilization of different microhabitats, reducing potential interspecific competition.