The taxonomic status of subspecies and species of Diptera Pupipara described from Japan and the Republic of Korea was investigated. Two subspecies of Hippoboscidae and three subspecies of Nycteribiidae described based on Japanese specimens are treated as new synonyms of respective nominotypical subspecies: Ornithomya avicularia (Linnaeus, 1758) (Syn. n.: O. avicularia aobatonis Matsumura, 1905); Ornithomya chloropus (Bergroth, 1901) (Syn. n.: O. chloropus extensa Maa, 1967); Nycteribia allotopa (Speiser, 1901) (Syn. n.: N. allotopa mikado Maa, 1967); Basilia rybini Hurka, 1969 (Syn. n.: B. rybini japonica Theodor, 1973; B. truncata Theodor, 1966 (Syn. n.: B. truncata endoi Mogi, 1977). Two species described from Korean specimens are treated as new synonyms: Nycteribia formosana (Karaman, 1939) (Syn. n. Nycteribia uenoi Maa, 1968); Nycteribia quasiocellata Theodor, 1966 (Syn. n. Nycteribia pleuralis Maa, 1968).