In this paper, a new approach to optimize the COP of a thermoelectric cooling module for a given cooling capacity is proposed. In the approach the heat flow at any axial location on a thermoelement is expressed by the temperature at that location, the electric current, the heat flow and the temperature at the cold end of a thermoelement and the properties of thermoelectric material, but not by the distance from the cold end to that location. In Section 2 the ideal model, in which the thermal and electrical contact resistances are neglected, is presented and the optimum current and the optimum thermoelement length to maximize the COP are obtained analytically. The more realistic model, in which the contact resistances are taken into account, is described and the procedure to obtain the optimum current and the optimum thermoelement length is proposed in Section