A method for mapping, by a base station, a channel state information reference signal (CSI RS) in a wireless communication system, and a user equipment (UE) for performing the method, are discussed. The method according to one embodiment includes selecting a resource element (RE) set from a plurality of RE sets in a subframe of a time division duplex (TDD) frame, wherein each of the plurality of RE sets includes a pair of consecutive orthogonal frequency division multiplexing (OFDM) symbol elements, and wherein the subframe uses an extended cyclic prefix (CP); and mapping the CSI RS to the selected RE set.