Two Russian children, a boy and a girl, were observed during the first steps of their use of diminutives. Having a different language proficiency and strategy of learning, the children under observation demonstrated a clear difference in the acquisition of diminutives: the early speaking girl Varja (as well as her mother) shows a high frequency of diminutives already at 1;6, whereas the later speaking Filipp reaches his maximum only about 2;0. It is argued that the most important pragmatic function of consciously used diminutives in cds as well as in cs is the creation of a familiar, personal world. The mothers try to familiarize the children with the surroundings, to make the world good for their children and to stress the relative smallness of the things that surround the children in contrast to those of grown-ups. Such distinctions are, in the Russian world, important both for the instruction and for the emotional comfort of a child. In addition, diminutives play an important role in facilitating the acquisition of case system: in the early phases both children use more indirect case forms of diminutives than of simplex nouns. This may be explained by the fact that diminutives end with similar codas. After children get a good command of using nominal case suffixes, this advantage of diminutives is of no help anymore.