The fragmentation of the natural habitat is a process that is exponentially increasing world‐ wide and represents one of the biggest threats to biological diversity. Habitat destruction and frag‐ mentation have a major impact on landscapes and may also affect ecosystems, populations, and spe‐ cies. The ongoing anthropogenic process can result in habitat loss for some species, habitat creation for others,reduced patch size, and increased distance between patches, which may lead to local extinction. We analyzed the effects of patch size and isolation on lichens in Quercus pubescens woods surrounding the city of Potenza (south Italy). We randomly sampled 11 forest patches with homogeneous environ‐ mental variables using circular plots with a 10 m radius; the patches ranged from 0.3 to 30 ha. For each plot, we collected data about presence and abundance of epiphytic lichens. We performed the analyses at the patch level using linear regression and multivariate analysis, searching for effects on species richness, life forms, and community compositions. Multivariate analyses were used to study the effect of fragmentation on the structure of lichen vegetation. We investigated the main predictor of lichen species richness in habitat fragmentations and concluded that patch area per se is an important (posi‐ tive) driver of lichen species richness in Mediterranean peri‐urban forests. Keywords: air pollution; epiphytic lichens; landscape ecology; Mediterranean ecosystems; Quercus pubescens forests; species richness.