Evaluating the sawlog quality is vital for both forest managers and wood processors. While external traits, such as tree form, branch architecture and visible growth features, can be evaluated through visual inspection, many key wood quality indicators remain hidden such as knot type and distribution, or the heartwood-to-sapwood ratio. This highlights the need for technologies capable of "seeing through" logs. Today, X-ray scanners in sawmills enable comprehensive, continuous, nondestructive assessment of internal stem structure at large scale. This study leverages a newly compiled database of approximately 726,000 scanned logs to characterize variability in knot distribution and sapwood proportion across three major European softwood species and estimate the moisture content. The analysis highlights inter-and intra-species differences. Sapwood proportion decreases with sawlog diameter in Spruce and Silver fir but remains high in Pine. Pine also presents significantly larger and more variable knots. Between March and August, we observed a seasonal trend in sapwood moisture content, affecting fresh density, while heartwood moisture content remained stable. These findings provide valuable information to support decision-making processes, linking tree characteristics to wood qualities and guiding forest management.