This paper disentangles the effects of uncertainty in explaining the heterogeneity of firms' investments. In particular, following Bloom (2007), we test the role of uncertainty and liquidity constraints extending the model to include R&D, non-R&D intangibles, as well as physical capital.The analysis is performed on a large dataset of Italian firms, covering both manufacturing and services sectors, as well as large and small firms. We show that non convex adjustment costs affect different capital inputs in different ways, depending on their degree of firm-specificity. The results confirm the Bloom model: flow adjustment costs explain investment in R&D and, to a lesser extent, in non-R&D intangibles. However, it struggles to explain tangible investment plans because of the ambiguous effect of the stock adjustment costs.