Enterprise social networks (ESN) make fast inroads into organisations. They are said to improve communication across silos and the capacity to collaborate and innovate. Yet, despite increasing academic interest, there is limited empirical research on what uses of ESN create value for individual users. To fill this void, we first report on results of a cross-case analysis into ESN communication patterns. We identify five prevalent activities of ESN users, which we use to derive constructs measuring ESN usage. We place these constructs as determinants of perceived value. We test our research model with survey data from active ESN users using partial least squares (PLS). The results show that the primary source of value derives from generating and obtaining ideas and new information as input for one's work. The study contributes to theorising ESN value and the nature of ESN systems.