The present study was focused on the assessment of genetic diversity in twenty-three populations of Orobanche cumana parasitizing on sunflower in Bulgaria Turkey Moldova and Romania using 13 ISSR markers. The obtained results on the genetic diversity parameters showed that the broomrape populations were characterised by a significant level of the intrapopulation diversity. In addition descriptive population genetic statistics revealed that Turkish populations had a higher level of genetic diversity indices than populations from several areas of the northeast and east of the Balkan Peninsula included in Eastern Europe. The analysis of molecular variance showed that 38 % of the genetic variability was due to differences within populations 34 % was due to differences among populations and the lowest molecular variation was among countries (28 %). According to clustering and PCA methods Moldavian Bulgarian and Romanian broomrapes shared more genetic traits with each other than with Turkish populations within a main gene pool. As a whole all results of this study showed that there is a high intrapopulation diversity of the O. cumana gene pool in the Black Sea basin. From the clustering and PCA analyses it can be concluded that the grouping of broomrape populations is partly determined by their geographical origin as well as by the genetic differences and similarities accumulated over time and is not related to virulence. The information obtained from this study may be highly relevant in contributing to the development of sustainable control strategies of the pathogen and breeding programmes for sunflower resistance to broomrape.