One of the major topics in the areas of microelectronics and communications today is the study of photonic band-gap (PBG) structures using planar transmission lines. In fact, structures using microstrip-line circuits have been comprehensively applied in recent years. However, studies involving transmission lines using striplines (STP) have not been commonly conducted. In this paper, a number of PBG structures constructed on the STP are studied by using a wellknown numerical method, the finite-difference time-domain (FDTD) method. Results show the band-stop filter behavior of these structures, and the computed results match generally well with the ones published in literature through solver validation. To improve the narrow bandwidth of regular PBG structures, a chirping and tapering technique is introduced. The proposed STP PBG structures may be considered as alternatives to the conventional microstrip-line typed PBG structures.