The Realization Optimality Theory is a recent development in the original Optimality Theory which is proposed to deal with morphological issues especially the inflectional ones. Its main idea is to consider the morphological realization rules as ranked violable language-specific constraints that control the realization processes and provide phonological information of grammatical morphemes. This article deals with the investigation of some morphosyntactic (inflectional) features of modern Persian in Realization Optimality Theory, and shows among the other things that it is a better model for treating inflection than the original Optimality Theory, but it still faces some problems with regard to a language like Modern Persian in which some morphosyntactic features are treated differently in formal and informal varieties, hence separate tableaux with different rankings of constraints are sometimes needed in order to select the optimal candidates in each of those varieties.
