Novel diplexer and dual-band filter using a squire open-loop with inset feeding and folded lines are proposed for wireless communication systems. These structures have a compact size. Simulations and experimental results have verified that these structures provide a good performance to be have single pair of transmission zeros at finite reel or imaginary frequencies. The bandpass filters utilizing open-loop having an inset feeding has more coupling characteristics than that of a filter realized employing conventional microstrip open-loop resonator. The modes in the pass-band and the location of transmission zeros can be easily controlled by inset deep, the length of the folded arms that they are coupled to each other by adjusting their length, and by relocating of resonators with two different forms. Consequently, two diplexers and two dual-band bandpass filters with adjustable transmission zeros are designed and realized to use in wireless communication systems.