Financing of research and development, as an important component of innovation, has attracted a renewed attention in academic financing literature. This paper examines the effect of financing constraints on R&D investments of high-tech Swedish companies over the period of 2010 to 2016. Accordingly, balance sheet data related to 49 companies, which has the smaller amount of employees in comparison with the rest of high-tech publicly listed companies is collected. Moreover, a dynamic model based on previous literature about financing constrained is developed to study the relation of both internal and external resources of financing with R&D investments of the selected companies. The result of this study shows that internal resources of financing such as cash holdings have a positive correlation with R&D investments. The coefficient of this financial variable is large enough to conclude that selected firms are financially constrained. However, based on other factors such as consideration of age and occurrence of global financial recession in the period that this study is accomplished, I concluded that dependence of companies to their internal resources for financing their R&D investments is an outcome of the characteristics of their environment.