Within a group of companies, a model is given for management of the relationships between the parent company and its subsidiaries. This is particularly relevant for groups originating from mergers and takeovers, because firms acquired often differ substantially in organizational structure from each other and from the parent company. The model provides a means of harmonizing the organizational structures of parent company and subsidiaries, so as to provide a complete coverage of necessary activities without duplication, and a means of identifying which activities should, in economic terms, be centralized by the parent company, and which should be delegated to the subsidiary. Finally, there is an empirical application of the model to one of the principal Italian banking groups.