The aqueous extracts (AEs) and the ethanolic extracts (EEs) prepared from some lichen species were evaluated for antiviral activity against human parainfluenza virus type 2 (HPIV-2) and cytotoxic activity towards Vero cells. MTT (tetrazolium blue) assay was used to evaluate the reduction of viability of cell cultures in presence and absence of the extracts and plaque assay was used to evaluate the antiviral activity. The AE of Xanthoria parietina (L.) Th.Fr. and the EE of Xanthoparmelia tinctina (Maheu & A. Gillet) exhibited attractive antiviral activities. The 50% effective concentration (EC50) of the AE of X. parietina for HPIV-2 replication was 10 6.3 mu g/mL, and the antiviral index (AI) was 50. The EC50 of the EE of X. tinctina for HPIV-2 replication was 20 2.8 mu g/mL, and AI was 22.5. In an effort to analyze further the mechanism of antiviral activity, the effectiveness of the AE of X. parietina and the EE of X. tinctina on different steps of virus replication leas examined. The antiviral activities of extracts could be attributed neither to the direct inactivation of the HPIV-2 nor to the inhibition of adsorption to Vero cells. These species are good candidates for further activity-monitored fractionation to identify active principles.