Many answer set solvers utilize Satisfiability solvers for search. SMT solvers extend Satisfiability solvers. This paper presents the CMODELS(DIFF) system that uses SMT solvers to find answer sets of a logic program. Its theoretical foundation is based on Niemela’s characterization of answer sets of a logic program via so called level rankings. The comparative experimental analysis demonstrates that CMODELS(DIFF) is a viable answer set solver.