Recently, corporate social responsibility (hereafter, CSR) of firms has become an important topic in all fields of business. The topic takes a greater importance in Korea which has accomplished rapid economic growth mostly from large companies. There are two opposing views, both theoretically and empirically, on the role of CSR. The first is the value-enhancing view of CSR, which argues that CSR activity is a positive NPV investment thus increasing firm value. A possible channel for this role of CSR is that so long as CSR promotes wealth increase of some stakeholders, these stakeholders will support the firm’s other business activities and contribute to the firm’s performance. The other view is the expense view of CSR, which argues that CSR is a manifestation of an agency problem and thus hurts firm value and shareholders’ wealth. Based on the expense view of CSR, managers can exploit CSR at the expense of shareholders in order to gain good reputation from other stakeholders. Based on these two opposing views of CSR, this study empirically examines the CSR activities of Korean firms in relationship to the degree of product market competition and the amount of R&D investment. As a proxy of CSR activity, we use the KEJI index provided by CCEJ as the dependent variable. Other main variables of this study are HHI (Herfindahl-Hirschman Index) to measure the degree of product market competition, and the amount of R&D investment, leverage and free cash flow of firms. Using firms listed in the Korea Exchange and those that are in the manufacturing industry, we perform various regression analyses including the Fama-MacBeth cross sectional regressions. The sample period of the study is between January, 2009 and December, 2015. Our main results of the empirical analyses are as follows. First, the degree of product market competition has a positive impact on the amount of CSR activities. This result supports the value-enhancing view of CSR. Second, the size of R&D investment also has a positive effect on the amount of CSR activities. This result supports the expense view of CSR. Third, the result with respect to the leverage and free cash flow variables, which are proxies of agency cost, is consistent with the expense view of CSR. Overall, results are more supportive of the expense view of CSR compared with the value-enhancing view of CSR. This implies that the CSR activies of Korea firms can be another showing of agency problem.