The effectiveness of buttresses and cross walls in reducing deflections of diaphragm walls in two cases is evaluated by studying the wall deflection paths and reference envelopes. Both sites are located in the K1 Zone of the Taipei Basin and excavations were carried out to a depth of 32 m by using the top-down method of construction. It has been found that cross walls were effective in reducing wall movements in these two cases. On the other hand, the effectiveness of buttresses was highly dependent on their configurations.