The present invention pertains to novel uses of glycyrrhetinic acid (GA), glycyrrhizic acid (GLA) and related compounds for prevention and/or treatment of pulmonary fibrosis, in particular, irradiation-induced pulmonary fibrosis. Also embodied are therapeutic uses of prodrugs, metabolites, derivatives (e.g., acids, esters and ethers), and salts of glycyrrhetinic acid (GA) and glycyrrhizic acid (GLA). The present invention also provides for therapeutic or pharmaceutical compositions comprising a compound of the invention in a form that can be combined with a pharmaceutically acceptable carrier.