1. A method for decoding motion vectors comprising: selecting a neighbor block having a motion vector used to obtain a predictive motion vector of a present block included in a macroblock according to a size and a location of the present block; and determining the motion vector of the neighbor block as a predictive motion vector of present block, wherein, if the present block is 8×16 and located in a left side of the macroblock, the motion vector of the neighbor block located in a left side of the present block is selected as the predictive motion vector of present block.