Two structures presenting an uncomplexed 2,6-diaminopurine (dap) group are reported, namely 2,6-diamino-9H-purine monohydrate, C(5)H(6)N(6)·H(2)O, (I), and bis(2,6-diamino-9H-purin-1-ium) 2-(2-carboxylatophenyl)acetate heptahydrate, 2C(5)H(7)N(6)(+)·C(9)H(6)O(4)(2-)·7H(2)O, (II). Both structures are rather featureless from a molecular point of view, but present instead an outstanding hydrogen-bonding scheme. In compound (I), this is achieved through a rather simple independent unit content (one neutral dap and one water molecule) and takes the form of two-dimensional layers tightly connected by strong hydrogen bonds, and interlinked by much weaker hydrogen bonds and π-π interactions. In compound (II), the fundamental building blocks are more complex, consisting of two independent 2,6-diamino-9H-purin-1-ium (Hdap(+)) cations, one homophthalate [2-(2-carboxylatophenyl)acetate] dianion and seven solvent water molecules. The large number of hydrogen-bond donors and acceptors produces 26 independent interactions, leading to an extended and complicated network of hydrogen bonds in a packing organization characterized by the stacking of interleaved anionic and cationic planar arrays. These structural characteristics are compared with those of similar compounds in the literature.