Molecular calculations were carried out with four different methodologies to study the CH4-nH(2)O complex, for n = 1-21. The HF and MP2 methods used considered the 0 atom with pseudopotential to freeze the 1S(2) shell. The other methodologies applied the Bhandhlyp and B3lyp exchange and correlation functionals. The optimized CH4-nH(2)O structures are reported, specifying the number and type of H2O subunits (triangle, square, pentagon, etc.) that comprised the nH(2)O counterpart cluster or cage, that interacted with the CH4 molecule, and, in the latter case, that provided its confinement. Results are focused to understand the stability of the CH4-nH(2)O complex. The quality of the electron correlation effect, as well as the size of the nH(2)O cage to confine the guest molecule, and the number and type of H2O subunits comprising the nH(2)O Cluster or cage are the most important factors to provide the stability of the complex and also dictate the particular n value at which the CH4 molecule confinement occurs. This number was 14 for the HF, Bhandhlyp, and B3Lyp methods and 16 for the MP2 method. The reported hydrate structures for n < 20 could be predictive for future experiments.