In the paper we establish the xed-parameter complexity for several parameterized decision problems involving models, supported models and stable models of logic programs. We also establish the xedparameter complexity for variants of these problems resulting from restricting attention to Horn programs and to purely negative programs. Most of the problems considered in the paper have high xed-parameter complexity. Thus, it is unlikely that xing bounds on models (supported models, stable models) will lead to fast algorithms to decide the existence of such models.