In this paper we compare findings from Norwegian-American heritage speakers to data collected from Norwegian-English bilingual children as well as Norwegian monolingual children. The focus is on two aspects of the Norwegian DP: word order in possessive constructions and modified definites requiring double definiteness. Our findings are discussed in relation to factors such as complexity, frequency and structural similarity/difference in the acquisition and attrition processes. We ask whether the same factors that affect the acquisition process in monolingual and bilingual language acquisition also are vulnerable to language attrition and thus shape the development of heritage languages. Our findings suggest that this is not the case. The data from the heritage speakers indicate that, unlike the children, they are more influenced by the frequency than the complexity of a structure. Furthermore, while the bilingual children’s production is affected by structural similarity with English, the heritage speakers in general seem to be more sensitive to the structural difference between the two languages. However, a small subset of the heritage speakers (three speakers) can be shown to behave in a manner similar to the bilingual children. We argue that these speakers are attrited speakers of heritage Norwegian, and that it consequently is necessary to distinguish between heritage speakers and attrited speakers.