Samsung and LG led the global market for ultra-high definition TVs with a combined market share of 51 percent during the July to September period.
The Korean tech giants were followed by Chinese TV maker Hisense and Japan's Sony, each with a market share of around 10 percent.
Market researcher DisplaySearch says the Korean firms are facing a growing threat from Chinese TV makers with cheaper products, adding that competition for the market is going to be fierce in the fourth quarter.