Inducing technological progress is an important objective of environmental regulation. We investigate under which conditions regulation-induced technological progress pursues the best technological option. We analyze a setting with vertical and horizontal technological progress, cost uncertainty, time-limited patent protection, and a case that is typical for some emissi4on-intensive industries, like electricity generation or the chemical industry. Under taxes and standards, only the current least-cost technology is used and developed, implying a lock-in into a possibly inferior technology. Tradable permits yield slower progress but can facilitate the simultaneous development of technologies, rendering lock-ins less likely.