In the last years, the business creation and management literature has paid increasing attention to the entrepreneurship that occurs within organizations. Most empirical studies show a positive relationship between corporate entrepreneurship and performance. The objective of this article is to identify which internal and external factors condition corporate entrepreneurship. The study uses two different theoretical perspectives: Resource-Based Theory (for internal factors) and Institutional Economics (for external or environmental factors). Both theories have been widely used in the strategic management and entrepreneurship literature, however, very few studies in the corporate entrepreneurship field are grounded on them together. The research applies negative binomial regression and uses data from the Global Entrepreneurship Monitor (GEM) for the period 2004–2008. Overall the sample has 339.071 observations and it provides information for 9 different European countries (Greece, Spain, Italy, Ireland, the Netherlands, France, the United Kingdom, Denmark and Finland). Results reinforce the importance of internal factors (knowledge, personal networks and being able to identify business opportunities) compared to external (having fear of failure, media impact and the number of procedures to create a company). Contributions of the study are both theoretical and practical. On the one hand, it contributes to the development of the literature in the corporate entrepreneurship field. On the other hand, it provides useful insights for those companies that are interested in entrepreneurship within the organizations.