This book constitutes the refereed proceedings of the 8th International Conference on Unconventional Computation, UC 2009, held in Ponta Delgada, Portugal, in September 2009. The 18 revised full papers presented together with 8 invited talks, 3 tutorials and 5 posters were carefully reviewed and selected from 40 submissions. The papers are devoted to all aspects of unconventional computation ranging from theoretical and experimental aspects to various applications. Typical topics are: natural computing including quantum; cellular, molecular, neural and evolutionary computing; chaos and dynamical system-based computing; and various proposals for computational mechanisms that go beyond the Turing model.