In a motor-vehicle seat a padding body of a cushion and/or backrest has a passage for air coming from an air conditioning system of the motor-vehicle. This passage includes a closed cavity defined between a lowered surface formed in an outer surface of the padding body and the seat cover. At least part of the closed cavity is separated from the cover through a layer of a material substantially impervious to air, configured to exchange heat by thermal conduction, through the cover with a body of an occupant.