Soil structure, especially its pore networks, affects many fundamental soil properties. Computing tomography (CT) provides a nondestructive means of observing soil pore structure and monitoring solute breakthrough in real-time. We investigated large undisturbed soil columns collected from two structured soils. Five positions (Ap1, Ap2, Bt, and two boundaries between horizons) were scanned at three different stages with 78.1µm×78.1 µm×86.7µm voxel size: 1) unsaturated, 2) saturated with water, and 3) injection of KI solution (as a tracer). Three dimensional pore volume, pore surface areas, pore hydraulic radius, tortuosity, connectivity, and fractal dimension were computed from the CT images. Preferential flow pathways were segmented based on the higher CT number for the tracer. Preliminary results showed obviously different flow patterns at the five positions in the soil columns. Preferential flow pathways were mainly related to the macropores, especially the wormholes and those connected to the wormholes. In addition, the interface between macropore and matrix domain was also active in solute transport. This study illustrates the significance of soil structure in better understanding and modeling of water flow and solute transport in naturally-structured soils.