An invention concerns a moisture control in a cryotherapy system and creating of snow mist. The system comprises a treatment chamber (102) for at lest one person, a closable entry (106) to the treatment chamber, and a cooling apparatus (108). The cooling apparatus comprises an evaporator (110) configured to function with a coolant (109) and a valve (111 ) for flow control of the coolant, wherein the evaporator (110) is placed in the treatment chamber and the valve is coupled to the evaporator. The system further comprises a ventilation aperture (112) for obtaining additional air (113) into the treatment chamber (102), the ventilation aperture (112) being placed far from the evaporator (110) to such spot that the additional air (113) flows from the ventilation aperture towards the centre of the treatment chamber (102) and simultaneously mixes with the air included in the treatment chamber so that water vapour of the additional air changes from gas to solid ice crystals and forms snow mist in the treatment chamber (102).
