The main goal of this study was to investigate the amounts of hydrophilic extractives in bark and wood samples of black locust stem (Robinia pseudoacacia L.). The concentrations of extractives were highest in the outermost samples of heartwood. Knotwood of black locust contained less DHR than heartwood. Significantly less hydrophilic compounds were extracted from bark and sapwood samples. This study shows that heartwood of black locust can be considered a source of value-adding compounds. The investigation showed significant variability in the content of extractives in a radial direction and less pronounced axial variability within the black locust stems.