Firms undertaking independent and cooperative research and development (R&D) activities simultaneously often have difficulties to enjoy the synergistic effects of these two types of R&D activities. This study contends that such difficulties are caused by tensions between independent and cooperative R&D activities in terms of resource competition and knowledge leakage. It then argues that organizational slack and absorptive capacity may affect these tensions and thus play critical roles in synergizing independent and cooperative R&D activities. Based on a survey data of 286 firms, it finds that such two types of R&D activities jointly have a negative effect on firm performance. Moreover, organizational slack contributes to generating synergies of independent and cooperative R&D activities, whereas absorptive capacity has an adverse effect. The findings not only enrich the discipline¡¯s knowledge regarding the interrelations between independent and cooperative R&D activities, but also shed some light on how firms can synergize them.