The paper empirically investigates the issue of financial constraints to investment, focusing on its relationship with innovation activities. The study is based on the analysis of a cross-industries panel of 804 Italian companies, observed through the years 1995-2000. The main objective of the study is to highlight whether there are financial determinants underlying the strong bias of patenting activity towards larger companies in the Italian economy. By applying a dynamic panel analysis, we found that only the firms showing lower financial constraints are able to keep a sustained patenting profile through time. Our evidence suggests the existence of an imperfect capital market in the Italian economy, particularly in the case of medium-sized companies, which tend to delay inefficiently the start of in-house R&D activities.