In today business world where knowledge and resources are increasingly spread among organizations, enterprises often develop a wide variety of relationships with other organizations in order to access new technologies, know-how and resources. Increasingly, the use of external resources for innovation – also referred as inbound open innovation in literature – is seen as a key factor to remain innovative and hence competitive. While the impact of open innovation on the firm’s innovativeness and performance has received quite some attention by scholars, the mechanisms that push firm to open up their innovation process remain under investigated. The aim of this paper is to contribute to fill in this gap by developing and testing empirically a research framework on the firm specific factors impacting the firm’s degree of openness. In order to reach the research objective, an extensive literature review was performed based on which several research hypotheses were developed. A web-questionnaire was then designed and distributed to the CEOs of food SMEs in Europe. A major result of this study is that network competence – defined as the firm’s ability to establish and use relationships with other organization – drives the firm’s openness in terms of ambidexterity (i.e. new versus existing relationships) and breadth (number of external sources or search channels that the firm relies upon in its innovative activities).