Résumé : Using public support as the baseline, the aim of the Ph.D. thesis is firstly to assess its effectiveness in alleviating firms’ financing constraints (Chapter 2) and in enhancing the innovation-growth linkage (Chapter 5), in comparison with other financing sources. Secondly, the research undertaken also explores public policy effectiveness in two periods of time: ex-ante and ex-post analysis. In the former, effectiveness is assessed according to whether the characteristics of the project selected for the subsidy are in line with the policy targets (Chapter 3). In turn, the ex-post analysis assesses firms’ effectiveness in achieving the planned goal and the sustainability of the achieved outcomes (Chapter 4). Chapter 2 provides evidence that, in addition to a guarantee for loans, measures to facilitate equity investments and making existing public measures easier to obtain could be considered as the main solutions for future financing. Tax incentives for financially constrained firms are revealed to be the least important factor. Chapter 3 aims to understand which kinds of projects are selected for an innovation subsidy and if the characteristics of the project selected are in line with the policy target. The results show the selection process seems to be particularly effective in meeting the goals as regards the amount of investment, as well as the expected effect on enhanced internationalization and productivity. Nevertheless, the study also reveals some failures in the selection process, namely in terms of the intensity of the project’s contribution to growth. Chapter 4 assess firm performance after project implementation. Results show that subsidized firms reached targets linked with employment level and sales more easily than labour productivity and value creation. Chapter 5 reveals that equity financing has a greater effect on the strategic decision to innovate and the highest output additionality on firm turnover growth. Grants have a more moderate effect on innovation and firm growth (both turnover and employment).