The paper analyzes the optimal structure of the board of directors in a firm with ownership concentrated in the hands of a large shareholder who sits on the board. We focus our attention on the choice between a one-tier board that performs all tasks and a two-tier board where the management board is in charge of project selection and the supervisory board is in charge of monitoring. We consider the case in which the large shareholder sits on (and controls) the supervisory board but not the management board. We show that a two-tier structure can limit the interference of large shareholders and can restore the manager's incentive to exert effort to become informed on new investment projects without reducing the large shareholder's incentive to monitor the manager. This results in higher expected profits in a two-tier board than in a one-tier board and the difference in profits can be sufficiently high to induce large shareholders to prefer a two-tier board despite the fact that in this case the manager selects his preferred projects rather than the project preferred by large shareholders. The paper has interesting policy implications since it suggests that two-tier boards can be a valuable option in Continental Europe where ownership structure is concentrated. It also offers support to some recent corporate governance reforms, like the so-called Vietti reform in Italy, that have introduced the possibility to choose between one-tier and two-tier structure of boards for listed firms.