A refrigerator includes a main body defining a compartment, the compartment having an access opening, a first wall and a heat exchanger supported by the first wall; a refrigeration system containing therein a working medium and including an evaporator which is disposed outside of the compartment for cooling the compartment; a door supported by the main body for selectively closing at least part of the access opening of the compartment; and a sub-compartment on the door and including a second wall with an opening. The heat exchanger is coolable by the working medium. The heat exchanger and the second wall are positioned so that when the door is in a closed position, the heat exchanger is exposed to an interior of the sub-compartment through the opening.