Carbon dioxide dissolution at intermediate ocean depths was studied using physical and mass transfer models. Particle density and hydrate layer thickness were determined using existing field data. Pseudo-homogeneous and heterogeneous mass transfer models were proposed to study the dissolution process. Pseudo-homogeneous models do not seem to represent the dissolution process well. Although heterogeneous models interpret the physical behavior better, unresolved issues related to hydrate dissolution still remain. For example, solid hydrate forms on one side of the hydrate film while it dissolves on the other. Dissolution is a complex process that comprises at least two sequential steps. The global process is controlled by mass transfer inside the hydrate layer or by a dissolution reaction at the hydrate-water interface. (c) 2005 Elsevier Ltd. All rights reserved.