Planting spacing plays an important role in tree growth and wood formation. Thus, the aim of this study was to determinate how planting spacing and genetic material affect the radial variation of basic density and chemical composition of wood. The sampling of this study was based on 4 clones of Eucalyptus urophylla × Eucalyptus grandis at 5 years of age planted in four spacings (3 × 1, 3 × 2, 3 × 3 and 3 × 4 m). To determine the basic density (BD), extractive (EXT) and lignin (LT) content, wood discs were removed at breast height, which were sectioned in three radial positions (pith, intermediate and sapwood). The results showed that genetic material, planting spacing and radial position affected the values of BD, EXT and LT content. The BD and EXT content tended to increase with increased planting spacing, while the LT content tended to decrease. In relation to the radial variation, the basic density showed an increase in the pith-bark direction, while the EXT content showed a decrease in this direction. For LT, no significant difference was observed in the pith-bark direction. In general, the largest planting spacings promoted the highest rates of variation of the properties studied.