It has been assumed that in articleless languages such as Russian, bare singular NPs in argument positions can receive a definite or an indefinite interpretation. While the definite interpretation depends on the broader discourse and may freely arise if the referent is familiar, the option of an indefinite interpretation for bare NPs introducing new discourse referents is more restricted. This paper investigates conditions on the indefinite interpretation of bare singular NPs in Russian. It shows that this interpretation is restricted by the topic-comment structure: the indefinite interpretation may arise only if the NP belongs to the comment part of the sentence and is excluded for NPs which are aboutness topics. This restriction can be explained by the requirement that indefinite aboutness topics must be specific. Bare indefinite NPs however can only receive a non-specific existential interpretation, and hence do not qualify as topics. The paper contributes to the elucidation of the interaction between the semantic and pragmatic components of an overall theory of NP interpretation and argues that weak existential NPs should be distinguished from cases of noun incorporation.