In the Upper Kolyma basin, the usually applied age criteria of relief-forming moraines of ancient mountain glaciers based on their heights are not valid and lead to the incorrect results which are included in the accepted stratigraphic correlations of Quaternary deposits of the region. More reliable and simple criterion of relative age of the moraines is proposed. It is age-related difference in the preservation state of the primary moraine relief, which has been long used on the planes. In two long-studied and one new test sites, we have investigated the morphology, location, composition of moraines, their interrelations, correspondence to the river landforms and alluvial deposits. As a result, three main morphologic groups of surface moraines were recognized: "fresh", "decrepit" and "smoothed" ones. The first and second ones correspond to the Last and Pre-last Late-Pleistocene glaciations, the third one - to both Middle-Pleistocene glaciations. These results may be used to more precise geomorphological and geological mapping of the territory, palaeogeographic reconstructions and planning of detailed palaeoglaciological researches.