Do the additionality effects of R&D tax credits vary across sectors? The paper presents a micro- econometric analysis of this question for three countries: Norway, Italy and France. We use a panel of firm-level data from three waves of the Innovation Surveys carried out in these countries for 2004, 2006 and 2008. The study estimates input and output additionality effects of R&D tax credits in each of these economies, and it investigates how these effects differ across sectors characterized by different R&D orientation and competition conditions. The results point out that firms in industries with high R&D orientation have on average higher propensity to apply to R&D fiscal incentives schemes and stronger input effects. Output additionality ...