We have studied theoretically the structure of complexes of water with the fluoromethanes and the contribution of hydrogen bonding. Hartree-Fock (HF) method, Density Functional and pertubational MP2 methods were used in order to account for correlation. Different basis sets were tested including 3-21G, 6-31G, 6-31G(d), 6-31+G(d) and 6-31++G(3df, 2pd). The Basis Set Superposition Error (BSSE) was taken into account using the Counterpoise Corrections. The optimized geometries were determined at HF, B3LYP and MP2 levels. The binding energies results suggest the influence of halogen substitution for the complex formation. We have also studied the energy partition for the complex formation. (c) 2006 Published by Elsevier B.V.