This study develops a framework of internal and external factors that influence the adoption of eco-innovation. We studied 80 adoption processes in the Dutch brewing industry and the Dutch paper industry and analysed the relative importance of different factors. We find that internal factors were more important than external factors. The analysis also shows differences between the industries. The financial advantage was important for both industries, but especially for the paper industry. For the brewing industry, ethical responsibility and stakeholders played a more important role in the adoption. The analysis also revealed differences for small and large firms. Ethical responsibility and stakeholders are relatively more often mentioned by small firms, whereas clear objectives and regulations were mentioned more by large firms. Our study highlights that the adoption of eco-innovation is a complex process and the position in the supply chain as well as the size of a firm influence what is important in the adoption of eco-innovation.