The genus Diplotaenia currently includes two species: D. cachrydifolia, providing the type of the generic name, is disjunctly distributed in N Iran and S and E Turkey; D. damavandica is a narrow endemic of the Elburs Mts, being sympatric in this region with D. cachrydifolia. Studies of the Diplotaenia material from Turkey showed that the Bitlis and Taurus populations are morphologically divergent from each other as well as from the Iranian populations of D. cachrydifolia and they are described as two separate new species, D. turcica and D. hayri-dumanii. Analysis of nrITS sequences of all four species of Diplotaenia and presumably related Umbelliferae taxa of SW Asia provide support for the monophyly of Diplotaenia and its placement in the Prangos-Ferulago clade, but revealed almost no differences among the species of Diplotaenia. The fruit anatomical analysis of Diplotaenia also supports an Apieae rather than a Peucedaneae relationship. A key to the four species of Diplotaenia is provided and the name D. cachrydifolia lectotypified.