The response function of a planar HPGe detector due to escape of photoelectrons and Compton-scattered photons was studied for a point source with 59.5 keV energy. It was shown that both mechanisms, in addition to Ge x-ray escape, leading to partial deposition of energy, could be observed in the same experiment. A Monte Carlo program was used to investigate these components of the response function. The results indicate that although the escape of scattered photons and Ge x-rays are of the same magnitude, the escape of photoelectrons plays a more important role in the efficiency of a detector. Copyright (C) 2003 John Wiley Sons, Ltd.