Abstract. Let R be a Noetherian ring and let C be a semidualizing R-module. In this paper, we impose various conditions on C to be dualizing. For example, as a generalization of Xu [22, Theorem 3.2], we show that C is dualizing if and only if for an R-module M , the necessary and sufficient condition for M to be C-injective is that π i (p, M ) = 0 for all p ∈ Spec (R) and all i = ht (p), where π i is the invariant dual to the Bass numbers defined by E.Enochs and J.Xu [8].