In this paper, we analyse empirically the effects of financial characteristics on the relationship between R&D investment and market value of firms listed on Korea Exchange. The main results of this study can be summarized as follows. Firm size increase the market valuation of R&D investment because it provides economies of scale, easier access to capital market, and R&D cost spreading. Market share also positively effects the relationship between R&D investment and firm value. Alternatively, free cash flow has a negative effect on the relationship between R&D investment and firm value because firms with high free cash flow could be tempted to use the free cash flow to undertake negative NPV projects. The dependence on external finance is a handicap negatively assessed by the market when firms undertake R&D projects due to the higher information asymmetry associated with this kind of project. Labor intensity has a negative effect on the relationship between R&D investment and firm value because the abnormal profits arising from R&D investment are diluted among employees. Capital intensity also has a negative effect on the relationship between R&D investment and firm value due to the greater financial constraints faced by capital intensive firms. In conclusion, several financial characteristics(firm size and market share) positively effect the relationship between R&D investment and firm value, while others(free cash flow, dependence on external finance, labor intensity, and capital intensity) exert a negative effect. Therefore, we conclude that the effectiveness of R&D investment depends on these financial characteristics.