The invention relates to internal measurement methods of mobile communication systems, more particularly how to arrange time intended for signal measurement for the mobile stations. In the method according to the invention the RSSI and OTD measurements are made from the same data collected during a certain period of time, whereby the same measurement data in a way is used two times in order to generate two different sets of measurement results. This saves the free time available during one frame, because it is not necessary to arrange separate measurement periods for the RSSI and the OTD measurements.