In the previous paper presented at the 11th SOR, Darmstadt 1986, the authors had shown that the Pareto optimal set of a multicriteria problem remains invariable if on the objective vector function operates a strictly monotone operator of strictly monotone kind. In the present paper we give new proofs of two main theorems of this result and we show that the invariance of Pareto optimal set takes place also in the case of a topological transformation of the problem's variables. A possible interpretation of the above results in decision theory is suggested.