Obsidians sources used by prehistoric people in the Omolon River basin and neighbouring areas of north-eastern Siberia were determined for 112 artefacts from 30 sites by the energy-dispersive X-ray fluorescence (ED-XRF) method. The main suppliers were the primary obsidian sources in both the Chukotka (Lake Krasnoe) and Kamchatka (Itkavayam, Payalpan and KAM-8) regions, with distances from sources to sites up to about 300-900 km in a straight line. For the first time, the transport of obsidian from Kamchatkan sources has been detected outside of this territory. The mechanism of obsidian transport was most probably by downthe-line movement, especially in the case of the Lake Krasnoe source.