The heterogeneity of microhabitats is an important driver of biodiversity. Therefore, conserving habitat heterogeneity at multiple spatial scales is essential to biodiversity conservation. This study investigates the effect and the conservation value of micromosaic heterogeneity provided by the heather (Calluna vulgaris) patches in an Eastern-European peat bog on the spider communities. We found that the heather patches strongly affect spiders; the species richness and abundance were higher in heather than in open bogs. Heather shrubs form a separate special microhabitat, which differs in structure, microclimate and litter quality, and has a significant positive effect on diversity of spiders. Furthermore, we collected smaller spiders and more web builders in heather sites than in control sites, presumably due to the different microhabitat structures and prey availability. However, habitat type did not affect the vertical microhabitat preference of spiders. The species composition of spider communities differed between the two microhabitat types. We identified seven significant indicator species in heather shrubs, whereas three species were significant indicators of control sites. The species richness and the presence of rare and endangered peat bog specialist spider species in heather patches highlight the high conservation value of peat bogs.