Task of radiation therapy is to destroy cancer cells by providing dose of ionizing radiation to the target tissue. Biological effects of ionizing radiation on more and more smaller structures of the cells are studied with the advancement of technology [1]. Field of nanodosimetry emerged in the beginning of 2000s with aim to measure absorbed dose in nanovolumes of the irradiated spot. Nowadays, simulation of the effects of ionizing radiation at the nanoscale is carried out using Monte Carlo method. However, there is a need to compare the results of simulations with the real measurements [2]. Therefore, there is need to develop a nanodosimeter – a device that can measure the dose at the nanoscale. First step can be search for nano-sized materials which are susceptible to radiation in a dosimetric way. Lead sulphide (PbS) nanodots embedded in thin-film zirconia (ZrO2) were studied. The ZrO2:PbS films were irradiated with 6MeV medical electron radiation with doses 0 – 10 Gy. Dosimetric correlation between changes in photoelectron emission properties from the films and dose of electron radiation was searched for. Advantage of the method of photoelectron emission is that the signal is provided only from 10-100 nm deep surface layer of the studied material [3]. Derivatives of the photoemission spectra showed that certain electron emission centers exist in the ZrO2:PbS films and there is a linear correlation between their concentration and dose of electron radiation. In order to use the ZrO2:PbS films repeatedly for dosimetric purposes, i.e. to irradiate them again, the films must be restored to their initial condition present before the irradiation. This was achieved by annealing them in vacuum (10-5 mmHg). It was shown that annealing the films at 150°C during 30min erased dose of electron radiation stored in them. It was also shown that this temperature did not destroy sensing properties of the ZrO2:PbS films and they could capture dose of electron radiation again after annealing.