A combined computational/experimental technique was developed to analyze the compressive elastic properties of a rigid organic foam. This technique combines X-ray computed tomography, image analysis, and large-scale finite element computations utilizing a new numerical technique. Predictions of Young's modulus were validated with uniaxial compression testing. Good agreement was obtained between imaging/finite element computations and experimental mechanical measurements within experimental error, and the limited knowledge existing on the solid material comprising the backbone of the foam. Using the new combined experimental/theoretical procedures, it was found that the predicted Young's modulus of the solid backbone differed by more than a factor of 100 % between two different grades of the foam, in accordance with the findings of other researchers. A significant variability of the backbone modulus was also found within the same grade. Density measurements identified the variability between different grades of foam and different as-received sample thicknesses within the same grade of foam.