The most common pathogen of the sunflower in the Republic of Moldova is the broomrape (Orobanche cumana Wallr.). The incidence of this pathogen varies yearly depending on environmental conditions, but it is constantly detected in the central and southern part of the country. Thus, our previous research indicates that approximately 60% of sunflower seeded areas in the southern region and approximately 47% in the central part of the country are affected by O. cumana. The effect of the infection on sunflower productivity varies greatly, from insignificant yield reductions to losses of up to 90%, depending on the intensity of the attack. The data were collected, during the years 2015-2020, from the fields of the Testing Stations of the State Commission for Plant Variety Testing, located in various pedoclimatic areas of the Republic of Moldova, as follows: North (Visoca, Pelinia); Center (Băcioi); South (Grigorievca, Svetlîi). The effect of O. cumana on the seed yields of sunflower hybrids, depends on hybrid tolerance to the weed and environmental conditions, The incidence of infection can vary for the same susceptible genotype from 37 to 1047 broomrape shoots per 100 host plants. The highest incidence of O. cumana was found in the localities from the south region, Grigorievca and Svetlîi with maximum values in 2016 and 2017. To estimate the effect of broomrape on sunflower seed yield, we compared the yield of six sensitive, most strongly affected hybrids, with the harvest of the same genotypes grown under similar climatic conditions, but in the absence of infection or insignificant degree of infection. Thus we can see that the strong affected hybrids with broomrape can cause a decrease in seed yield of up to 52%. The rate of decline is not necessarily correlated with the number of broomrape shoots per 100 host plants.