Quantitative non-invasive imaging has evolved rapidly in the last decade, and is now being used to assess a variety of problems in vadose zone research, including unsaturated flow and transport of water and contaminants, macropore-dominated processes, soil-water-root interactions, more recent work on colloidal processes, and significant work on NAPL-water interactions . We are now able to use non-invasive imaging to probe processes that could not previously be quantified because of lack of opacity, resolution, or accurate techniques for quantitative measurement. This work presents an overview of recent advances in x-ray microtomography techniques that can generate high-resolution image-based data for (1) validation of pore-scale multi-phase flow models such as the lattice-Boltzmann technique and pore network models (with respect to fluid saturations, fluid distribution, and relationships among capillary pressure, saturation, fluid-fluid interfacial area, etc.), and (2) making the link between tomographic data and more traditional laboratory-based soil/vadose zone characterization such as hydraulic conductivity, air permeability, and pycnometer-based porosity measurements). Finally, limitations and advantages of these various approaches, as well as tomography specific issues such as resolution vs. REV requirement, access to the different types of equipment, etc. will be discussed.