This thesis examines one specific construction (the possessor raising construction) as an example of "optional" case marking in Korean from the perspective of optimality theory.  In traditional theory, the main function of the case markers is to assign/determine the grammatical role of the NP in a clause.  The relationship between the case marker and the grammatical role is mainly regarded as one-to-one mapping such as subject-nominative case marker, object-accusative case marker, possessor-genitive case marker etc.  When the possessor is marked with the accusative case marker in Korean (the so-called possessor raising construction), this one-to-one mapping fails.  This unusual case marking is recognized as being conditioned by 'inalienability', 'affectedness' and 'entailment' (Kim 1999; Kang 1998; Cho 2002).  However, I claim that the genitive case marker, the accusative case marker, and the zero case marker can each optionally occur with the possessor in the possessor raising construction, even where the possessor satisfies these three conditions.  The key concept is that the interaction between the grammatical role and information status of the NP provides the proper form of case marking for the possessor.