By finding the epiproct slide preparation of the holotype of Nemoura sahlbergi problematica Zwick, 1973, which was considered to be lost, the identity of the taxon is resolved. It is raised to species rank, Nemoura problematica Zwick, 1973 stat. nov., and Nemoura jilinensis Zhu & Yang, 2003 is considered as its junior synonym. The species is widespread in the Korean Peninsula, known also from NE China (Jilin Province) and the Russian Far East (Khabarovsk and Primorsky Krai). New Korean records are listed, its distribution is detailed and depicted on map. Nemoura sahlbergi Morton, 1896 is known from the Russian Far East but not from China and Korea.