A fire-extinguishing system for helicopter decks (10) comprises nozzles (24, 25) for the supply of foam or water to the helicopter deck and to a helicopter and the like placed on the helicopter deck. At the outer edge of the helicopter deck, just by a submerged gangway (13), and preferably also across the helicopter deck in or by an associated drainage duct (29), there is permanently arranged a conduit system (21, 22, 23) for foam or water, equipped with a first and a second set of nozzles. A first set of nozzles is adapted to direct a jet of foam or water of relatively low strength and relatively small range towards its respective established region of the helicopter deck in order to squirt or spray the same with foam or water. A second set of nozzles is adapted to direct a jet of foam or water of relatively high strength and relatively long range substantially in a direction towards the center of the helicopter deck.