Retention forestry is a commonly used approach to include biodiversity conservation in forest management of production forests. Tree-related microhabitat (TreM) assessment is suggested as a good practice for the selection of habitat trees to retain. TreMs are small structures on living or dead trees that provide living substrates, shelter, breeding places, or food sources for various groups of organisms, therefore, they can be a good indicator of the presence of forest-dwelling species. However, the knowledge linking bryophyte and lichen species diversity with TreMs is still scarce. In this study, TreMs and bryophyte and lichen species composition were assessed on living retention trees in 39 young forest stands (10–20 years post-cut) in Latvia to test whether the richness of epiphytes on retention trees up to 2 m height is related to the number of TreM types. There was a strong positive correlation between the total number of TreMs and lichen richness on Betula pendula (Rs = 0.66; p