The delay time of nanosecond electromagnetic pulses is measured in multiwalled carbon nanotube (MWCNT) bundles and copper wires, with a length of up to 3 cm, as compared with that in standard coaxial cables of the same lengths. Under certain configurations, when the Cu core of a coaxial: cable is replaced with a MWCNT bundle of the same length, the measured delay time of a pulsed signal is shortened. The difference between the delay time measured for a device with a Cu core and that of a device with a MWCNT bundle of the same length increases the length of the samples. The results imply that, compared with Cu wires, MWCNT bundles may be more efficient in guiding the transmission of high-frequency signals along their longitudinal axis, showing a waveguide-like effect.