Abstract The essential oils hydrodistilled from the aerial parts of Echinacea purpurea (L.) Moench grown at the Herb Garden of Casola Valsenio (Ravenna, Italy) from healthy and infected (cucumber mosaic cucumovirus; CMV) plant materials, were analyzed by GC/MS. The oil from healthy material was rich in germacrene D (57.8%) and was more abundant. The infected materials afforded a lower oil content and significant quantitative variations in the oil composition. In particular, the observed percentage of germacrene D (52.6%) was reduced as were other sesquiterpene hydrocarbons. These variations, tested to be significant for all the compound-class fractions and individual major components, were ascribed to the CMV infection, the only fixed-effect variable that might affect the oil composition.