<p>This paper deals theoretically with the entropy of mixing from solutions of a pair of linear oligomers and their cyclic counterparts as well as corresponding polymers using the honeycomb lattice model proposed by Léonard. The effects of various parameters, such as the architecture, size, rigidity and composition, on the entropy of mixing of the systems under consideration are investigated; the results obtained show mainly that this property of mixing is always weaker, as compared to that corresponding to linear molecules. This agrees with the observation made by di Marzio and Gibbs, according to which the cyclization induces a lowering of the total number of configurations of a cyclic molecule below the maximal number associated with a flexible linear chain. This discrepancy between a cyclic oligomer and its linear counterpart increases with the volume fraction but it decreases with the degree of oligomerization.</p>