The Platylomia radha species group is proposed within the genus Platylomia Stal, which includes one new species, Platylomia duffelsi sp. nov., ftom the north Vietnam. Synonymic lists for the four species of Platylomia ftom Vietnam are provided. A key to the four Platylomia species: P. bocki (Distant), P. duffelsi sp. nov., P. malickyi Beuk, and P. operculala Distant ftom Vietnam is provided. Photos of the adult, illustrations of the male genitalia. a distribution map and biological data are also given.