The Ybycuí National Park (PNY) is an important area for conservation of representative samples of the forests from the central zone in the Eastern Region of Paraguay. The aim of this study is to identify genera and families of lichens found in the forests of the reserve. Two semi-deciduous forested communities were selected, one riparian and one non-riparian. Only samples of corticolous lichens were collected. Specialized literature was used for the taxonomic identifi-tions and the lichen substances wERE studied through specific colour reactions using chemical rea-gents such as potassium hydroxide, sodium hypochlorite, fluoresCence in ultraviolet light chamber, and thin layer chromatrography. Forty-six species were identified, distributed in 21 genera and 13 families. The interior forest turned out to be more diverse than the riparian forest, with 28 species, 17 genera, and 11 families.