Pressure vessel (1) with a gas-impermeable liner (2) and a reinforcing layer (4) in composite material formed externally around the impermeable liner (2), as well as at least one boss (5) coupled to the impermeable liner (2) and to the reinforcing layer (4), wherein between the impermeable liner (2) and the boss (5) a polymeric sealing mass (7) is arranged bound to both the impermeable liner (2) and to the boss (5) by means of in situ cross-linking of the sealing mass (7).