A pressure vessel (4; 4') comprising: - a liner defining an internal fluid storage chamber and having: • a generally cylindrical central portion having a first outer diameter D1 at a first longitudinal end, • a first dome-shaped longitudinal end having a base of a second outer diameter D2, the second outer diameter D2 being smaller than the first outer diameter D1, and • a first intermediate portion located between the generally cylindrical central portion and the first dome-shaped longitudinal end and connecting the first longitudinal end of the generally cylindrical central portion to the base of the first dome-shaped longitudinal end, wherein said first dome-shaped longitudinal end of the liner has a dome contour which is less concave toward the internal fluid storage chamber than a dome-shaped longitudinal end having a geodesic dome contour, - a first dome reinforcement shell having a shape complementary to the shape of both the first dome-shaped longitudinal end and the first intermediate portion of the liner, the first dome reinforcement shell being fitted on both the first dome-shaped longitudinal end and the first intermediate portion of the liner, - a boss, and - an outer composite structure enclosing or encasing the liner, characterized in that the outer composite structure further encloses or encases the first dome reinforcement shell. - a liner defining an internal fluid storage chamber and having: • a generally cylindrical central portion having a first outer diameter D1 at a first longitudinal end, • a first dome-shaped longitudinal end having a base of a second outer diameter D2, the second outer diameter D2 being smaller than the first outer diameter D1, and • a first intermediate portion located between the generally cylindrical central portion and the first dome-shaped longitudinal end and connecting the first longitudinal end of the generally cylindrical central portion to the base of the first dome-shaped longitudinal end, wherein said first dome-shaped longitudinal end of the liner has a dome contour which is less concave toward the internal fluid storage chamber than a dome-shaped longitudinal end having a geodesic dome contour, • a generally cylindrical central portion having a first outer diameter D1 at a first longitudinal end, • a first dome-shaped longitudinal end having a base of a second outer diameter D2, the second outer diameter D2 being smaller than the first outer diameter D1, and • a first intermediate portion located between the generally cylindrical central portion and the first dome-shaped longitudinal end and connecting the first longitudinal end of the generally cylindrical central portion to the base of the first dome-shaped longitudinal end, - a first dome reinforcement shell having a shape complementary to the shape of both the first dome-shaped longitudinal end and the first intermediate portion of the liner, the first dome reinforcement shell being fitted on both the first dome-shaped longitudinal end and the first intermediate portion of the liner, - a boss, and - an outer composite structure enclosing or encasing the liner, characterized in that the outer composite structure further encloses or encases the first dome reinforcement shell.