Clean technologies implemented by polluters subject to environmental regulation are often developed and patented by specialized technology suppliers. This paper investigates the impact of the environmental regulation stringency on the diffusion of patented clean technologies when the polluters (i.e. the potential licensees) compete in imperfectly competitive markets. We show that the polluters' willingness to pay for clean technology and the diffusion of such technology (i.e. the extent to which it is privately disseminated through licensing) depend not only on the regulatory stringency and the technological efficiency, but also on the polluters' competitive environments. More stringent regulations (e.g., higher carbon taxes) or increased technological efficiency (e.g., supported by more R&D subsidies) do not necessarily induce more diffusion of efficient clean technologies. Indeed, as the returns to implementing a clean technology increase, so do the technology supplier's incentives to sell fewer licenses so as to extract more rent from each of its licensees.
