This research presents theory that formalises, and generalises to tasks in well-structured and ill-structured problem areas the role of the application domain in IS problem solving, thus opening the way to furthering knowledge on this important aspect of IS problem solving. The dual-task problem-solving model that forms the overarching framework for the theory was inspired by research on dual-task interference in cognitive psychology. The true contribution of this model lies in the use of the theory of cognitive fit to determine the different types of interactions that may arise.