Plant parasites of the genera Longidorus Micoletzky, 1922 and Paralongidorus Siddiqi, Hooper and Khan, 1963 comprise a group of plant root ectoparasites, some of which are known as pests of economic importance. Their importance is further augmented by the fact that several species are known to be vectors of nepoviruses. To date 16 species from the genus Longidorus and two from Paralongidorus have been recorded in Poland. Despite their economic importance in agriculture currently there is no regional key for species identification. This paper presents such a key. The key has many illustrations and is based mainly on traits which are easily observable even by less experienced users. Thus, it should provide a useful tool for both scientists and specialists working in the field of plant protection, soil ecology and zoology as well as for teaching purposes.