This paper develops an empirical approach using econometric techniques for panel data which aims to contribute to the reduction/elimination of the deviation between the book and market value of firms. Based on 20 of the firms with the largest number of patents granted between 1996 and 2006, the results show that: (i) the increase in the return on equity following from an increase in the share of investment in R&D is greater in the long run; (ii) there is a positive relationship between the results (and the value of firms) and R&D activities; (iii) by updating the additional periodical results generated by investment in R&D, the present value of the intangible asset can be determined.