The Korea Emissions Trading Scheme, set up in 2015 to cut carbon emissions in South Korea, ran into problems quickly. It allows trading of carbon credits on an exchange and over-the-counter. After its launch, the exchange market lacked liquidity, and over-the-counter credits were priced higher than exchange-traded ones, going against normal expectations. The article investigates why this happened, looking at the reasons behind the unusual price difference and the trading issues. By understanding what went wrong in the Korean carbon market, other countries thinking of similar systems can avoid pitfalls and make better choices.