Sunflower broomrape Orobanche cumana W allr . is a rapidly growing threat to the oil crop production in many countries. Fast adaptation to new environments and increasing host resistance suggests that phenotypically distinctive populations of the weed may have evolved. The classification of the species and the differentiation of such populations on the base of seed micromorphological characters were attempted. Morphometric measurements allowed the distinction of O. cumana from several other Orobanche and Phelipanche species. An irregularly thickened cell wall of the anticlinal testa cells differentiated O. cumana and O. cernua from O. caryophyllacea O. crenata O. minor P. aegyptiaca P. arenaria and P. ramosa . However populations of sunflower broomrape from five European countries and China could not be separated from each other on the base of micromorphological seed characters. In contrast length to width measurements indicated that the Asian samples had a slightly different seed shape which was less elongated than the European samples. However this seemingly geographic effect may as well be a consequence of sampling which comprised a higher rate of the so-called modern races E-H in the European samples.