In this communication, equilibrium conditions of clathrate;hydrates of cyclopentane, cylcohexane, acetone, or 1,4-dioxane + methane, which form structure II, and 1,1-dimethylcyclohexane, 2,2-dimethylpentane, methylcyclohexane, or cis-1,2-dimethylcyclohexane + methane, which form structure H, are modeled. The thermodynamic model is based on the van der Waals-Platteeuw solid solution theory combined with an equation of state and activity model. The Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) equations of state with random mixing rules are used to model the gas phase, while the UNIFAC method is used to model the liquid phase(s). It is shown that the use of the PR equation of state leads to better predictions of hydrate equilibrium conditions of the aforementioned water-insoluble heavy hydrocarbons, while the use of the SRK equation of state causes better predictions of hydrate equilibrium conditions of the latter water-soluble hydrate formers.