The radiolytic stability of hydrophobic extracting compounds CyMe 4 -BTBP and CyMe 4 -BTPhen and a hydrophilic masking agent (PhSO 3 H) 2 -BTPhen, widely employed for trivalent minor actinoid and lanthanoid separation, against γ radiation was tested. Even though the solvent with a promising fluorinated diluent BK-1 provides better extraction properties compared to octan-1-ol, its radiation stability is much lower, and no extraction was observed already after an absorbed dose of 150 kGy (CyMe 4 -BTBP) or 200 kGy (CyMe 4 -BTPhen). For the (PhSO 3 H) 2 -BTPhen hydrophilic masking agent, the results showed that the rate of radiolytic degradation was significantly higher in 0.25 M HNO 3 than in 0.5 M HNO 3 . For both the hydrophobic and hydrophilic agents, degradation was slower in the presence of both organic and aqueous phases during irradiation.