The experimental electron density distribution (EDD) in 8-hydroxyquinoline cocrystallized with salicylic acid, 1, has been determined from a multipole refinement of high-resolution X-ray diffraction data collected at 100 K. The experimental EDD is compared with theoretical densities resulting from high-level ab initio and BHandH calculations using Atoms in Molecules theory. 1 crystallizes in the triclinic crystal system, and the asymmetric unit consists of a neutral salicylic acid molecule, a salicylate anion, and an 8-hydroxyquinolinium cation exhibiting a number of inter- and intramolecular hydrogen bonds and pi-pi interactions. Topological analysis reveals that pi-pi interactions are of the "closed-shell" type, characterized by rather low and flat charge density. In general, the agreement of the topological values (rho(bcp) and Delta(2)rho(bcp)) between experiment and theory is good, with mean differences of 0.010 e angstrom(-3) and 0.036 e angstrom(-5), respectively. The energetics of the pi-pi interactions have been estimated, and excellent agreement is observed between the relative. energy and the strength of pi-stacking derived from the Espinosa approach, with an average difference of only 4.4 kJ mol(-1).