The study was aimed to evaluate the impact of extraction solvent on the phenolic content, total flavonoids content, and the antioxidant activities of acetonic, methanolic, and aqueous extracts of two lichen species: Evernia prunastri and Ramalina lacera collected from trunks of Argania spinosa using the ultrasound assistance extraction. Various in vitro antioxidant assays were utilized such as 2,2-diphenly-picryly-hydroxyl free radical (DPPH) assay, and ferric reducing antioxidant power (FRAP) assay. All tested samples exhibited a good antioxidant activity, for the DPPH assay, the inhibition percentage ranged from 85±0.2% to 27±0.01%, the phenolic content ranged from 13.17±0.5 mgGAE/g DW to 3.31±0.3 mgGAW/g DW, and flavonoids ranged from 5.84±0.03 mgRE/g DW to 0.01±0.03 mgRE/g DW. This study demonstrates that the extraction solvent has a significant influence on lichens phenolic compounds and on their antioxidant activity, also showed that flavonoids contents are significantly correlated to antioxidant activity of studies lichens; moreover, it shows that ultrasound extraction in a good method to extract the lichens compound. This study suggests that lichens Ramalina lacera and Evernia prunastri could be utilized as natural antioxidant source. [ABSTRACT FROM AUTHOR]