The Item Response Theory (IRT) is a psychometric theory world wide used in education evaluation and cognitive psychology. Along with the increasing of this theory's application, new issues with great practical importance arise, like considering the Differential Item Functioning (DIF). Because of the need of IRT generalization by models that consider these important issues, two IRT models that consider DIF existence are proposed. They are both generalizations of the three parameters logistic model and differ from each other on the hypothesis of knowing which items have DIF, that is: one of them incorporate DIF detection. It is presented a Bayesian approach based on MCMC methods for the inference procedure. Later, simulated studies with both models are presented in order to study their characteristics and the efficiency of the Bayesian methods on the parameters estimation. Finally, it is also presented an example with real data concerning an educational program in the state of Rio de Janeiro, Brazil.