A seat portion of a vehicle seat has a padding, which is covered with permeable upholstery defining a user supporting surface and has a plurality of chambers extending crosswise to the supporting surface; the chambers are open at their ends and, in use, vary in volume in response to oscillating movement of the user; the chambers are grouped in at least four groups, which are located, respectively, in front right, front left, rear right, and rear left position; the chambers of each group are isolated in fluidtight manner by the chambers of the other groups and communicate with a respective opening, which connects the lower end of the chambers to the outside; the opening of each group is associated with a respective valve, which operates independently from the valves of the other groups and is opened/closed automatically in response to compression and decompression of the air in the chambers.