In plants, phase change from the juvenile stage to maturity is a tightly controlled process at the physiological and genetic level, which is controlled by evolutionary highly conserved microRNAs. These phase changes are more pronounced in woody plant species, but the majority of molecular genetic studies on the regulation of this transition has been done in annual model or crop species. This process is of particular significance for the in vitro propagation of woody plant species, as individuals or tissues that have undergone the transition to vegetative maturity are recalcitrant to propagation. Development of effective methodologies for silver birch vegetative propagation are required to increase the efficiency of breeding programs. Conserved miRNAs that were differentially expressed between juvenile and mature silver birch tissues were identified using high-throughput sequencing of small RNA libraries. These differentially expressed miRNAs could potentially be utilized to develop markers indicating the juvenility or maturity of silver birch explants and in vitro cultures. In addition, the obtained results will provide an insight into the molecular mechanisms regulating vegetative phase change in silver birch and other perennial woody plant species.