Functors which are determined, up to natural isomorphism, by their values on objects, are called DVO (Defined by Values on Objects). We focus on the collection of polynomial functors on a category of sets (classes), and we give a characterization theorem of the DVO functors over such collection of functors. Moreover, we show that the (-bounded) powerset functor is not DVO. Key words: category of sets (classes), set functor, inclusion preserving functor, DVO functor.