<p>The objective of this study was to investigate the influence of calcium fertilization on wood structure and density of <i>Eucalyptus grandis</i> trees grown in two different commercial plantations in Colombia. Wood samples were collected from trees grown at two different sites and were fertilized with calcium at different application rates variants. Wood density was determined using stereometric methods and X-ray computed tomography (CT), while diameter at breast high (dbh) measurements were taken to assess tree diameter. The wood microstructure were examined using image analysis software, optical microscopy, and scanning electron microscopy (SEM). Additionally, Fourier-transform infrared (FTIR) spectroscopy was employed to investigate spectral differences in wood composition. The results indicated that neither plantation site nor calcium fertilization treatment significantly affected wood density. The average density was 522 ± 27&#xa0;kg/m³. X-ray CT analysis revealed radial variation in wood density, with higher density towards the pith and lower density towards the bark. Dbh measurements demonstrated significant differences between samples from the two sites, which are hypothesized to be attributed to site specific conditions rather than fertilization. Microstructural analysis unveiled consistent radial variation patterns in fiber wall thickness and vessel diameter regardless of the origin of the wood.</p>