Polyanionic DNA can bind electrostatically with cationic lipids to form a complex used for gene delivery and nanostructure construction. Here, we reveal two multilamellar phases, L-I and L-II, characterized by distinct states of lipid packing and DNA conformation in a DNA/cationic lipid complex in the bulk state. The L-II phase, formed when the lipids are in excess of DNA in terms of overall ionic charge, is composed of B-DNA confined between the bilayers with the lipid tails aligning normal to the lamellar interface. When DNA becomes in excess of the lipids, the L-I phase in which the DNA is bound with the tilted lipid chains adopting the A conformation is favored because this configuration offers more economical electrostatic binding between these two components.