This paper presents the algorithm for validation of electrodes locations for the thoracic impedance measurements. In particular the presented algorithm was designed to perform the telemetric sleep apnea monitoring. One of the problems, during the clinical tests of a developed device, was to preserve the repeatability of measurements. It strongly depended on the appropriate electrodes placement on the examined person's thorax. It seems that the developed software, which allows inspecting the electrodes localization, significantly increases a possibility of impedance based sleep apnea monitoring at home. In this article, the properties of the evaluation algorithm of electrodes placement accuracy are presented.