The main purpose of the article is to empirically validate a hypothesis derived from the so-called Melitz (2003) model that there is a positive relationship between the productivity of companies and their export propensity, using firm-level data for Poland. In addition, the study attempts to endogenize the productivity of firms by referring to their spending on research and development (R & R), use of human capital and new technology. The empirical results obtained by the authors confirmed the predictions of the Melitz (2003) model regarding the presence of a positive relationship between the productivity of companies and the probability of exports in the case of Polish companies. In addition, the attempt to endogenize the productivity of companies showed that the probability of exports can be influenced by the level of expenditure on R&D and the use of the internet, while the proportion of skilled workers in employment did not prove to be statistically significant. On the other hand, the size of the firm was an important determinant of export activity. The larger the firm the greater is the probability of it exporting its products and services, the authors say. The study also showed that the internationalization of firms, measured with the use of foreign technology licenses and foreign ownership, is positively correlated with the probability of exporting. The authors’ results are thus consistent with those obtained previously in other large European Union countries.