Core-functionalized star-shaped polymers consisting of linear poly(methyl methacrylate) arms and a microgel core with functional groups were found to act as efficient hosts for selective interaction with small organic molecules as guests. For example, star polymer I with an amide-functionalized core (M-w = 1.21 x 10(3); DP(arm) = 100; 71 arms/molecule; -NH-CO-in the core) could interact with benzoic acid, benzyl alcohol, and benzylamine, whereas such interaction was absent with acetophenone, ethyl benzoate, and amylbenzene, indicating that the interaction stems from hydrogen bonding between the host's amide core and the guest. Thus, polymer I specifically interacts with benzoic acid in an equimolar mixture of the acid and its ethyl ester. The host-guest interaction is inhibited by polar solvents such as DMF and by acids like CF3CO2H.