This book is an account of the variation between two possessive constructions in Danish and Swedish: the s-genitive (husets tak ‘the house’s roof’), and the prepositional construction (taket på huset ‘the roof of the house’). Present-day corpus data, as well as historical data (texts from 1250–1550) are explored. Through statistical and qualitative analysis, various factors that influence the choice between the two constructions are identified. The book offers new data on the genitive variation in Danish and Swedish. The approach is also novel as two closely related Scandinavian languages are compared from both a historical and a contemporary perspective.