The paper aims to show how regional policy-makers can stimulate firms' co-operation with research organizations by granting an R&D subsidy. Using an original dataset for the Italian region of Emilia-Romagna, propensity score matching is first applied to identify the impact of the subsidy received. A generalized propensity score technique is then employed to investigate the effect of an increasing amount of support. The firm's co-operation is policy sensitive. The award of a subsidy to regional firms affects their intra-regional more than their extra-regional co-operation. The propensity toward the latter appears subject to a monetary effect and is influenced by the amount of public funding received providing the subsidy overcomes a minimum threshold.