A device for containing fluid substances under airtight conditions and dispensing them, comprising a rigid container (5) in which a bag (9) made of thermoplastic material is inserted having a flange (3, 3A) and a hole for housing the body of a (P), the body of the pump (P) being pressed to form a seal on said flange (3, 3A) of the bag (9) by a first ring cap (N), a second ring cap (G) being screwed onto the container neck (6) and secured to the bag (9), the first ring cap (N) being locked to the second ring cap (G), engagement means (13, 14) being provided between said first and second ring cap to make said first and second ring cap torsionally rigid with each other such that a rotation imposed on the first ring cap (N) of the pump results in a corresponding rotation of the second ring cap (G), hence facilitating extraction of the bag from the container consequent on the removal of the pump (P) from the container (5).