The invention relates to a side protection device for a vehicle comprising at least one side airbag (10) that protects a vehicle occupant in the event of side collision of the vehicle. In order to achieve a particularly high degree of safety for the vehicle occupants to be protected, the invention provides that the side airbag has an outflow opening (50) through which the gas can exit the side airbag, and/or has an overflow opening (130) located inside the airbag, and after the side protection device has been tripped, the side airbag is inflated and positioned laterally next to the vehicle occupant (30) in such a manner that the outflow opening and/or the overflow opening are/is closed according to the body size, is throttled with regard to its flow of gas or remains open.