A coplanar waveguide (CPW) fed Ultra Wideband (UWB) slot antenna with reconfigurable rejection bands is presented. Specific band of the rejection is achieved by placing switching diodes over the rectangular slot in the ground plane at a position of effective length of λ/2 for the center frequency of the rejection band. The rejection of WiMax, IEEE 802.11a and HYPERLAN/2 bands can be achieved by switching the diodes. The simple configuration and low profile of the proposed antenna leads to easy fabrication that may be used in any wireless UWB device applications where reconfigurable rejection bands are required.