Crystal structures of five imidazolin-5-ones are discussed. While molecules 1-3 show a donor-acceptor type of $\pi \cdots \pi$ lateral offset stacking, C-H$\cdots \pi$ interactions are found to play dominant roles in molecules 2 and 4. In molecule 2, C-H$\cdots \pi$ interactions further form lateral offset stack to form extended C-H$\cdots \pi \cdots \pi \cdots$H-C hydrogen bonds. Molecule 4, however shows a layer structure with interlayer C-H$\cdots \pi \cdots $H-C hydrogen bonds and interlayer stacking of imidazolin-5-one heterocycles. These structures show how weak $\pi \cdots \pi$ interactions can be exploited for tailoring supramolecular assemblies.