This paper proposes a self-healing approach to handle exceptions in service-based processes and to repair the faulty activities with a model-based approach. In particular, a set of repair actions is defined in the process model, and repairability of the process is assessed by analyzing the process structure and the available repair actions. During execution, when an exception arises, repair plans are generated by taking into account constraints posed by the process structure, dependencies among data, and available repair actions. The paper also describes the main features of the prototype developed to validate the proposed repair approach for composed Web services; the self-healing architecture for repair handling and the experimental results are illustrated.