Developing non-destructive, high precision characterization methods of pattern cross section is critical to the maturation of sub-65 nm technologies. In this study, Criticial Dimension Small Angle X-ray Scattering (CD-SAXS) data are used to non-destructively characterize the dimensions of dense, high aspect ratio patterns with sub-nm precision. Data are presented for a series of photoresist patterns with varying degrees of footer and sidewall angle. The scattering intensity, I, is measured as a function of the scattering vector, q, and the sample rotation angle, w. The resulting data are transformed to an effective Qx-Qz plane, representing the Fourier transform of the average pattern cross section. From this data, complex features of cross sectional shape can in principle be obtained through systematic analysis of appropriate intensity slices. Here, we demonstrate the protocol for high precision measurements using CD-SAXS. Data are analyzed to extract average values of pitch, line width, line height, sidewall angle, and the size of a foot or undercut. In addition, the ability of the technique to analyze more complex features, such as lines with curved sidewalls and corner rounding, is discussed. The CD-SAXS technique is found to provide dimensions with sub-nm precision and sidewall angles with sub-degree precision in a non-destructive manner, providing an option for characterization of next generation microelectronic and nanofabricated structures.