This paper addresses the role of R&D cooperation with external partners in companies implementing inbound and outbound open innovation. The results of the survey of 206 companies show that the cooperation with external partners is different in companies implementing inbound, outbound, and coupled open innovation compared to closed companies oriented towards internal R&D. Increased importance, success, and intensity of cooperation with external partners are observed for companies with internal R&D and inbound, outbound, and coupled open innovation compared to other firms. The more a company implements open innovation, the higher the intensity, importance, and success of cooperation with external partners are. The importance and success of cooperation with domestic partners is higher than for cooperation with foreign partners for all types of companies.