In 2008, Korea Fair Trade Commission ("KFTC") found SK Telecom's acquisition of Hanaro Telecom anti competitive on the ground that SK Telecom's market dominant power in the wireless market could be transferred to the landline market by means of bundling of the products of the concerned parties. Based on such finding, KFTC issued corrective orders to SK Telecom such as restrictive measures on its bundling policy and compulsory roaming for 800 MHz band radio frequency. This decision is based on KFTC's merger guidelines which appear to have been influenced by the portfolio theory and entrenchment theory developed in US and modified in EU. However, such theories overemphasized anticompetitive effects of a conglomerate merger and underestimated its efficiency effects. Such theories have lost its influence in US since late 1970s and even EU authority, which championed such theories in late 1990s and early 2000s, has gradually changed its views in its recent cases and its Non horizontal Merger Guidelines promulgated in 2007. As pointed out in EU guideline, when reviewing a conglomerate merger, the competition authority should focus on its anti competitive effects that may be caused through tying or bundling rather than criticizing a conglomerate merger as a whole based on the portfolio theory or entrenchment theory. KFTC's decision on this case correctly raised concern about potential abuse of market dominant power through bundling, but it is not completely free from the outdated way of thinking influenced by portfolio theory or entrenchment theory.