A method and apparatus for encoding/decoding an image by using an extended skip mode are provided. The method includes setting a backward reference block motion vector with respect to an adjacent block of a current block as a predictive motion vector of the current block or determining a predictive motion vector from a forward reference block motion vector with respect to a block located in a backward reference picture at the same position as the current block, performing motion compensation by using the predictive motion vector, and setting a prediction mode when the motion compensation results in satisfaction of an optimal skip condition.