Disclosed herein are a video decoding method and apparatus and a video encoding method and apparatus. Coding decision information of a representative channel of a target block is shared as coding decision information of a target channel of the target block, and decoding of the target block is performed using the coding decision information of the target channel. Since the coding decision information of the representative channel is shared with an additional channel, repeated signaling of identical coding decision information may be prevented. By means of this prevention, the efficiency of encoding and decoding of the target block or the like may be improved.