This study claims that policy makers may not be sufficiently aware of the importance of maintaining an appropriate balance between exploration and exploitation networks for small and medium-sized enterprises (SMEs). On the basis of the open innovation model, policy makers are also increasingly stimulating SMEs to develop their exploration skills. In the Netherlands, a government subsidy called the 'innovation voucher programme' was introduced to stimulate SMEs to develop innovation in cooperation with knowledge institutes. Yet, although many studies show that SMEs tend to have a higher R&D productivity than larger firms, and innovative SMEs are more likely to make external networks with other SMEs or institutions such as universities, there is still little examination of the successfulness of SME's innovation activities. The growing policy attention for the role of SMEs in innovation prompts the questions how innovation in SMEs can be facilitated, and which factors contribute to the success (or failure) of their innovation efforts. This study explores the innovation strategy of innovative Dutch SMEs by means of their sources of innovation, innovation capabilities, innovation performance, and commercialization sources. By means of structural equation modelling of a sample of 243 Dutch SMEs, this study shows that exploring (technology) opportunity together with institutions such as universities and private research establishments is important for successful innovation in SMEs. But, in addition, our model shows that contacts with competitors are also important for successful innovation performance. Our finding that openness of open innovation also applies to the commercialization phase is too often neglected by researchers and policy makers. © 2012 The Author(s).