In this paper the studies on separation of some dicarboxylic acids (oxalic acid, malonic acid, succinic acid and adipic acid) by reactive extraction with Amberlite LA-2 in butyl acetate were continued. Thus, the conditions for a selective extraction were settled. The individual selective extraction is not possible because of the comparable values of acidic constants for oxalic and malonic acids, on the one hand, and for succinic and adipic acids, on the other hand. In this case, only selective extraction of oxalic and malonic acids can be achieved. For a high selectivity, both a molar ratio of 0.9-1 between the strong dicarboxylic acids (oxalic and malonic acids) and the extractant and a concentration of Amberlite LA-1 lower than the stoichiometric value for all acids extraction are required.