The present invention relates to a wireless communication system, and more specifically, disclosed are a method and an apparatus for transmitting or receiving a downlink signal by considering an antenna port relationship. A method for user equipment decoding an enhanced physical downlink control channel (EPDCCH) in the wireless communication system, according to one embodiment of the present invention, comprises the steps of: determining from a downlink subframe a reference element (RE) on which the EPDCCH is mapped; and decoding the EPDCCH based on the RE on which the EPDCCH is mapped. At least one EPDCCH-physical resource block (PRB)-set for monitoring the EPDCCH can be established for the user equipment, wherein a parameter set for each of the at least one EPDCCH-PRB-set is indicated by an upper layer, and the RE on which the EPDCCH is mapped can be determined based on the parameter set indicated by the upper layer.