The thermoreflectance technique is applied for imaging electric current distributions and thermal transfer in a temperature reference resistor heated by an alternating current. High‐frequency scans (30 kHz) allow imaging of the current density distribution in conducting strips of the resistor while scans of amplitude and phase of the surface temperature variation at lower frequencies reveal plane, cylindrical, and spherical thermal waves. We investigate wave dimensionality as a function of heating geometry and thermal length, and present a simple method allowing a quantitative thermal analysis by exploiting the phase profile of cylindrical thermal waves. ©1996 American Institute of Physics.