A handheld electronic device is provided that contain wireless communications circuitry. The wireless communications circuitry may include antenna structures. A first antenna may handle first and second communications bands. A second antenna may handle additional communications bands. The first and second antennas may be located at opposite ends of the handheld electronic device. Conductive structures in the handheld electronic device may form an antenna ground plane. The antenna ground plane may have portions defining an antenna slot. An L-shaped antenna resonating element may be located adjacent to the slot. In the first communications band, the L-shaped antenna resonating element may serve as a non-radiating coupling stub that excites the antenna slot. In the second communications band, the L-shaped antenna resonating element may transmit and receive radio-frequency signals.