Cucurbituril (or cucurbit[6]uril, CB[6]), a macrocycle comprising six glycoluril units, has been employed in the construction of a wide variety of interlocked molecules, and rotaxane-based molecular machines and switches. The recent discovery of cucurbituril homologues containing a different number of glycoluril units has further widened the scope of cucurbituril chemistry. In terms of cavity size, CB[6], CB[7], and CB[8] are analogous to α-, β-, and γ-CD, respectively. CB homologues share characteristic features of CB[6], such as a hydrophobic cavity, and polar carbonyl groups surrounding the portals. Therefore their varying cavity and portal sizes lead to remarkable molecular recognition properties. CB[6] forms very stable complexes with protonated diaminoalkanes (NH3(CH2)nNH3 , n = 4-7, K > 10 M) and moderately stable complexes with protonated aromatic amines such as p-methylbenzylamine (K ~3 × 10 M). On the other hand, CB[7] forms complexes with larger guest molecules that are not included in CB[6]. For example, CB[7] forms a 1 : 1 complex with 2,6-bis(4,5-dihydro-1Himidazol-2-yl)naphthalene (BDIN). It binds protonated adamantylamine as well as the methyl viologen dication (N,N'-dimethyl-4,4'-bipyridinium, MV) in a 1 : 1 ratio. Neutral molecules such as ferrocene and carborane are easily encapsulated in CB[7] in aqueous solution. The cavity of CB[8] is large enough to include two BDIN molecules to form a 1 : 2 complex, or another large macrocycle, such as cyclen and cyclam. During the course of these works, we noticed that the binding modes between the CB homologues and their guest molecules are differentiated according to the size of the hydrophobic part of the guest molecules. Herein we report the different binding interactions of CB homologues with a simple guest molecule, the 1,4-xylylenediammonium derivative 1. Depending on the cavity size of the CB, complexation led to [2] or [3]pseudorotaxanes (Figure 1).