New aromatic dithiophosphinic acids (R2PSSH) with R = C6H5−, ClC6H4−, FC6H4−and CH3C6H4−were synthesized, characterized and tested as potential separating agents for trivalent actinides over lanthanides. The extraction of Am(III), Eu(III) and other lanthanides was carried out from nitric acid medium with mixtures of R2PSSHS and neutral organophosphorus compounds. There was no detectable extraction when R2PSSHS were used alone as extractants for either Am(III) or Eu(III) (DAM,EU.< 10−3) under the experimental conditions used in this study. High separation factors (DAM/DEU> 20) with DAM> 1 were achieved in the nitric acid range 0.1-1 mol/L by means of a synergistic mixture of bis(chloro-phenyl)dithiophosphinic acid + tributylphosphate (TBP), irioctylphosphine oxide (TOPO) or tributylphosphine oxide (TBPO). The high radiation resistance (up to 106Gy absorbed γ-doses) of the extractants was also demonstrated.