Case markers in Korean are omissible in colloquial speech. Previous discourse studies of Caseless bare NPs in Korean show that the information structure of zero Nominative not only differs from that of overt Nominative but it also differs from that of zero Accusative in many respects. This paper aims to provide a basis for these semantic/pragmatic properties of Caseless NPs through the syntactic difference between bare subjects and bare objects: namely, the former are left-dislocated NPs, whereas the latter form complex predicates with the subcategorizing verbs. Our analysis will account for the facts that (i) the distribution of bare subject NPs are more restricted than that of bare object NPs; (ii) bare subject NPs must be specific or topical; (iii) Acc-marked NPs in canonical position tend to be focalized.