Kraft pulping is the current foundation for the manufacture of several biobased products. However, in order to meet the growing demand for pulp, it may be necessary to diversify the feedstocks used in the process and increase its resource efficiency.In this work, the behavior of three hardwood species that could potentially be applied in the kraft process was investigated. Birch (Betula pubescens), alder (Alnus glutinosa) and aspen (Populus tremula) were subjected to two sets of experiments. In the first, model chips of each species were subjected to batch kraft pulping applying a range of conditions (145-165 °C, 0.25-2.00 mol HO- / kg liquor), in order to evaluate how delignification and xylan removal progress in these samples. The second experimental set focused on comparing the microstructural features of these hardwoods and how they evolve throughout pulping. This analysis was conducted using in situ synchrotron X-ray microtomography (beam energy = 22.5 keV, 0.65 μm pixel size), by mounting a small reaction cell on the ForMAX beamline at the MAX IV Laboratory. The samples were treated under the same conditions (141 °C, 0.25 mol HS- / kg liquor, and 0.55 mol HO- / kg liquor) and fifteen measurements were taken for each sample throughout the reaction time (4 h).While only small differences in delignification rate were observed, the gradients of residual lignin and xylan within the samples varied significantly among the hardwoods. Aspen displayed the most uniform delignification and xylan removal, followed by alder. Such results seem to reflect the differences in morphology between the species, as evidenced by the imaging analysis through the comparison of cell wall thickness, lumen size and porosity during pulping.