I suggest to go around and try any of the numerous Korean restaurants along the street. It's one of the best ways to experience the distinguished flavours of Korean dishes and will provide you with an unique experience... but don't expect to find an English menu!
Also, whether it's Chinese, Italian or German, every dish has more or less been "Koreanized", i.e. don't expect to find hometown spaghetti or fried rice. In Itaewon, however, are some quite authentic restaurants from all over the world.
As Koreans can not survive without their traditional Kimchi, you can expect to find Kimchi as side-dish in any sort of restaurant... I even found a Kimchi-Pizza... simply everywhere.
Nevertheless, Seoul offers almost everything... check-out the following web-site to find your favourite dish: http://www.wguides.com/city/81/subsub_92.cfm
