Compact planar loop antennas fed by coplanar striplines (CPS) are presented for dual-band and ultrawideband (UWB) operations. The dual-band antenna consists of two resonant radiating parts, namely a strip loop and a slot loop. Based on the dual-band design, a wideband operation can be achieved. Two prototype antennas operating at the 2.4/5 GHz wireless LAN bands with dimensions of 45 × 15 × 0.813 mm3 and for the lower UWB band (3.1-4.8 GHz) with dimensions of 34 × 13.5 × 0.813 mm3 were fabricated on a RO4003 substrate. The measured input reflection loss is lower than 15 dB for the dual-band antenna and 10 dB for the UWB antenna. Both of the antennas show accept able gain and dipole-like radiation patterns over the operating frequency bands.