We have investigated the interactions of the lanthanum cation (La3+) with cucurbit [6]uril (Q [6]) and its alkyl-substituted derivatives (SQ [6]s), including symmetrical tetramethylcucurbit [6]uril (TMeQ [6]), symmetrical dicyclohexanocucurbit [6]uril (1,4-DiCyHQ [6]), and percyclohexanocucurbit [6]uril (CyH6Q [6]), as well as the supramolecular assemblies formed with the aid of inorganic anions (NO3− and Cl−) as structure-directing agents. Single-crystal X-ray diffraction analysis has revealed that the interaction results in the formation of three kinds of coordination complexes. The main driving forces may be the ion-dipole interaction of inorganic anions and the electropositive outer surface of Q[n].