Selyakov Orion R&D Association, 46/2, Enthuziastov shosse, Moscow, 111123, Russia E-mail: ayusel@mail.ru The capacitance-voltage characteristics of MIS-structures based on epitaxial n-Hg0.77Cd0.23Te taking into account the degeneracy and non-parabolicity at various approximations of values of integrals of the Fermi—Dirac were calculated. <...> The capacitance of tunneling via a trap for the MIS-structures based on n-Hg0.775Cd0.225Te was estimate. <...> As a result of the numerical solution of Poisson's equation constructed of capacitance-voltage characteristics of MIS-structures based on HgCdTe with near-surface graded-gap layer. <...> It is shown that the account of presence of gradedgap layer is necessary for correct interpretation of experimental data. <...>