Oh, I also wanted to mention Lotte department store. The one by Myeongdong, although I assume that other locations would be the same, is very high class. First floor is all uber nice brands, like Gucci and Yves Saint Laruant (not positive on that spelling). Next floor up is very expensive stuff... sorry, can't remember brands.. all I know is that I was seeing shirts for more than 300,000 won, and a fur jacket for 1,500,000 won. Third floor was all nice brands like Tommy Hilfiger and Polo Ralph Lauren and Club Monaco. There was at least one more floor, probably more, but I couldn't bring myself to go any further up.
Oh, and while you're in the area of Myeongdong, you should walk a few more blocks and you'll find yourself in Namdaemun market. This is a more traditional market with lots of bargaining with street sellers. (actually, this area reminded me alot of Patronato in Santiago, but with much tighter streets and a bigger variety of things to buy.) Hopefully I'll have a post about Namdaemun someday when I have more time to explore. I did manage to buy myself a set of ten (Korean.. aka metal) chopsticks... since somehow my apartment doesn't have a single pair.