This study provides a patent-based framework, investigating the relationship among the relevance of the technological domains, the exploitation vs. exploration strategies and the choice of open innovation practices. Specifically, this work presents five levels of open innovation adoption and analyses the reason why firms open up their innovation boundaries. The methodology is tested on a sample of 240 companies belonging to the bio-pharmaceutical and the technology hardware & equipment industries, by examining their patents filed in 2011. Results show that the relevance of the knowledge domain affects the choice of the innovation strategy; also, non-equity alliances are preferred in explorative activities and equity alliances in exploitative ones.