The author states the occurrence of harvest mouse (Micromys minutus (Pallas, 1771)) and hazel dormouse (Muscardinus avellanarius (Linnaeus, 1758)) in the East Slovakia based on summer nests from field margins, hedgerows, and woodland edges. A total of 791 (551 M. minutus and 240 M. avellanarius) nests from 71 localities were observed over the years 2013–2021. The total elevation range of these sites was between 110 – 560 m a.s.l., with different ratio recorded for both species. For M. minutus 15 plant species and for M. avellanarius 16 plant species were confirmed, with different dominance of their use. A statistically significant difference was confirmed by Mann-Whitney U test comparing both species for two common plants i.e., Prunus spinosa L. (U = 866.0, p = 0.012) and Rubus plicatus Weihe & Nees (U = 1103.0, p ˂ 0.0001). Moreover, Spearman’s correlations confirmed significant relationships between the positions of nests and plant height. At the same time, 12 individuals of M. minutus and 8 individuals of M. avellanarius were confirmed dead or escaping directly from their nests. Analysis of the composition of the leaves in the M. avellanarius nests showed the following proportions. Leaves of the three species R. plicatus (66.2%), Carpinus betulus L. (14.5%), and P. spinosa (8.3%) were most common in mixed nests. For foliar nests, a ratio of two dominant species, R. plicatus (50.0%) and C. betulus (41.6%), was recorded. Finally, for the layered nests, a ratio of two dominant species, R. plicatus (50.0%) and C. betulus (33.3%) was recorded. The obtained data help spreading knowledge of both species in the territory of Slovakia.
