We analyze the potential of different knowledge stocks to decrease the technological gap between the leader in green technology inventions and its followers in order to identify if wait-and-see is a reasonable option to benefit from knowledge. Our econometric results indicate that it is difficult to decrease the technological gap and remain competitive in the generation of green technologies without timely accumulating green knowledge. Although effects from external green knowledge stocks also contribute to decrease the technological gap, the effects are moderate and they cannot compensate the lack of internal green competences. Non-green knowledge stocks even tend to increase the technological gap.