Plant biomass and metal shoot accumulation are key factors for efficient phytoextraction. In a previous study, chemical mutagenesis has been used to improve the phytoextraction potential of sunflowers. The main goal of the present study was to assess the stability of sunflower mutants with improved biomass and metal accumulation properties in the 3rd and 4th generations. As compared to control plants, the best M3 mutants showed the follwing improvement of metal extraction: Cd 3-5-fold, Zn 4-5-fold, and Pb 3-5-fod. The best M4 sunflowers also shoed enhanced metal extraction: Cd 3-4- fond, Zn 5-7-fold, Pb 6-8-fold and Cr 5-7-fold. The control sunflower inbred line IBL 04, grown directly ion the field, accumulated metals in individual organs in the following decreasing order: Cd and Zn: leaves > stem > roots > flower > seeds; Cr: roots > flower > seeds > leaves > stem. The best sunflower mutants showed either higher metal accumulation in shoots or enhanced metal accumulation in roots, suggesting to improved phytoextraction or rhizofiltration efficiency, respectively.