Abstract. Schmidt proved that an operator T from a Banach lattice E into a Banach lattice G with property (P ) is order bounded if and only if its adjoint is order bounded, and in this case T satisfies |T | = |T | . In the present paper the result is generalized to Banach lattices with Levi-Fatou norm serving as range, and some characterizations of Banach lattices with a Levi norm are given. Moreover, some characterizations of Riesz spaces having property (b) are also obtained.