Limiting molar conductances (∧o) of Ph4PBPh 4, Bu4NBPh4, Bu4NNO3, Bu4NClO4, Bu4NBr, Bu4NI, Ph 4PBr, NaBPh4, AgClO4, AgNO3, LiNO3, NaNO3, KNO3 and NaBr have been determined in DMF-DMSO mixtures at 25, 35 and 45°C using Shedlovsky conductance equation. Limiting molar ionic conductances (λ io) have been calculated from λo(Ph 4P+) ≅ λo(Ph4B -) assumption. Discussion of effective ionic radii (ri) ... [Show full abstract] calculated from λio values is based on ion-solvent interactions. The results indicate the existence of electrostatic ion-solvent interactions in the case of alkali metal cations via O atom of both the solvents and specific interactions between Ag+ ion and DMSO via S atom of S=O group of DMSO molecule. The latter is found to be in agreement with the concept of soft acid-base type of interactions. Association constants (KA), however, yield no significant contribution.