The aim of our investigations was to search the reasons of survival of ragweed plants after herbicide treatments. Therefore ragweed achenes (later referred as seeds) were collected from those sunflower fields, which were treated with imazamox, tribenuron-methyl and glyphosate herbicides. TTC test was used to determine seed viability. Seed were sown under glasshouse conditions and their germination was evaluated continuously. Young ragweed plants were treated with normal and double dose rates of imazamox, tribenuron-methyl and glyphosate – with the same herbicides which were applied under field conditions before seed collection. Phenological and symptomatological observations were carried out continuously. 52 days after treatments the green biomass of ragweed plants was measured for each pots. It was stated that tribenuron-methyl – independently from the origin of ragweed seeds – significantly retarded the development of ragweed plants as compared to untreated control ones, but treated plants did not die. Ragweed populations showed sensitivity or moderate sensitivity to normal and double dose rates of imazamox. The effectivity of glyphosate was 100% in case of each ragweed population. Future investigations are necessary to collect seeds from the survived plants from more arable fields and to clear the reason of (partial) unefficiency of herbicides. Furthermore it is important to examine that – in case of partial unefficiency – the plants are able to flower and produce seeds which may play role in the transmission of resistance.