The organization of start-ups contests by large mature firms appears as a growing practice to stimulate corporate entrepreneurship. We explore this phenomenon to characterize the mutual benefits for large firms and start-ups. We show the influence of two factors on the nature of the relationship between large mature firms and start-ups. The first is the product oriented or service oriented innovation processes of large firms. The second is the distance between the core technological fields of large firms and start-up. Based on these two factors we propose a categorization of start-ups contests in four types: early co-development, co-development close to market, acceleration and outsourcing. The cases we study show the strong influence of the technologies linked to Internet in the development of the start-ups contests. Accelerating programs that accompany the practice of start-ups contests rely on the creation of private accelerators that play an important role as boundary spanners and gatekeepers.