Abstract: The starting point of integrated information theory (IIT) is that consciousness (subjective experience) exists, immediately and indubitably, and that the purpose of a scientific theory of consciousness is to account for subjective experience in objective, physical terms. IIT does not presuppose that consciousness arises at the level of neurons rather than atoms, molecules, or larger brain areas, but instead predicts that consciousness emerges at the level of organization at which the intrinsic causal powers of a system are maximized. IIT thus assumes causation to be a central concept of the theory from the microphysical to the macroscopic. However, it remains to be determined whether IIT as a theory of consciousness is compatible with quantum mechanics as a theory of micro physics. Here, I will present recent efforts to extend IIT’s causal framework to quantum systems and discuss several conceptual challenges that arise around the notion of measurement, and the identification of causal entities in separate branches of the wave function. Finally, I will briefly outline how the emergent ontology implied by IIT escapes epiphenomenalism, while being agnostic about the causal closure of the physical.