Abstract
Many companies claim they are adopting an open approach to innovation, but each of them with its own way. This paper explores the different models for opening up the innovation process adopted in practice, by means of an extended survey among Italian manufacturing companies. The study in particular distinguishes different open innovation models with respect to two variables, representing the degree of openness: (i) the number and type of partners with whom the company collaborates and (ii) the number and type of phases of the innovation process actually open to external collaborations. The study shows that four models are adopted, corresponding to four clusters of companies: open innovators, closed innovators, integrated collaborators and specialised collaborators. The paper describes each cluster in terms of firmspecific variables that affect, characterize and support open innovation choices; at last, it tries to draw some tentative explanation of the influence of openness on the innovative performance of companies.