A computational method for coherent electron transmission versus energy and Ohmic conductance versus frequency, for a diode with an arbitrary potential profile, is applied to resonant tunneling. For a symmetrical double-barrier structure, when the Fermi level is at a resonance energy the conductance falls off at a frequency equal to the half width of the transmission peak divided by Planck's constant, while for the non-symmetrical structure with the same well width it rises from the smaller zero-frequency conductance to a strong peak at about this frequency before falling off. When the Fermi level is displaced from the resonance energy, the dependence is more complicated. All cases have the same asymptotic half-width/frequency dependence. For a resonance transmission peak of a "quantum wire" with a smoothly varying disordered potential, a result similar to the non-symmetrical diode case was found. © 1990.