Abstract: A pressure tank for storing gas, for mounting in a gas-operated vehicle. The pressure tank has a rotationally symmetrical, elongate shape which is cylindrical in the central region and is closed at both ends by curved polar caps, and a wall which surrounds a hollow space for storing the gas. At each of the polar caps, the pressure tank has a metallic connection piece, a so-called boss. The wall has a reinforcing layer made from fiber-reinforced plastic and an inner liner for sealing purposes. For sealing purposes, a bush is connected to the boss. A pressure ring and a spring element are configured in such a way that the spring element is supported on the bush and presses the pressure ring against the liner and, as a result, presses the liner in a region against the boss.