A potential alternative to conventional disk-loaded copper structures is dielectric-loaded accelerating (DLA) structures, which comprises a simple geometry where a dielectric tube is surrounded by a conducting cylinder. The simplicity of the DLA structure offers a great advantage for RF-driven (> X-band) accelerating structures as compared with conventional metal structures which demand extremely tight fabrication tolerances. The detailed geometry optimizations for DLA structures are presented in this talk. Different commercial software CST and HFSS are used to calculate the RF parameters for both DLA structures and Iris-loaded CLIC accelerating structures and relevant results are shown in comparison. In addition, the wakefield studies on DLA structures are also included in this talk.