We analyse the problem of the choice of the market variable in a model where firms activate RD investments for process innovation. We establish that (I) firms always choose the Cournot behaviour; and (ii) there exists a set of the relevant parameters where a benevolent social planner prefers quantity setting to price setting. This happens when the marginal cost of RD activities is relatively low while technological externalities are relatively high. In this situation, the conflict between social and private preferences over the type of market behaviour disappears.