Abstract: DNA and RNA molecules both serve as genetic material inside viruses but the structure of packaged RNA molecules remain elusive. Moreover, RNA has more diverse functional roles than DNA. Differences between DNA and RNA duplexes are most evident upon addition of a condensing agent, such as the trivalent ion cobalt hexammine (CoHex). Under conditions where DNA condenses into insoluble precipitates, RNA molecules remain in solution (Physical Review Letters 2011, 106, 108101). In fact, x-ray scattering experiments suggest that in the presence of CoHex, short RNA helices form end-to-end stacked soluble structures. We study the physical origin of nucleic acid condensation by comparing four 25 base-paired helical constructs: DNA, RNA and a DNA-RNA hybrid of similar sequences and a homopolymeric DNA sequence. Recently, we used UV spectroscopy and Circular Dichoism (CD) to connect condensation propensity to spatial location of CoHex ions determined from molecular dynamics simulations (Nucleic Acids Research 2014, 42, 10823). Here, we use solution x-ray scattering to examine the pre-condensed phase and explore conditions that might effectively condense and package RNA.