EMISA 2009 is the 3rd International Workshop on Enterprise Modelling and Information Systems Architectures. The workshop offers a platform for researchers and practitioners working on all different aspects on modeling of enterprises and architectures of information systems. Furthermore, the workshop brings together people from different areas such as computer science, business computer science, and information systems. The selective review process guarantees high-quality publications. Further information can be found on http://www.uni-ulm.de/in/iui-emisa09.