A plastic pressure vessel comprises a first (1, 2) and a second part (2, 1) welded to each other. The first part (1) comprises a layer (11) of thermoplastic material having substantially continuous fibres. The second part comprises a layered structure having an first (20) and a second (22) layer of thermoplastic material having substantially continuous fibres separated by a central (21) layer comprising thermoplastic material. The layer having substantially continuous fibres (11) of the first part extends over a length (d) sandwiched in between and connected with the first (20) and second (22) layer of thermoplastic material having substantial continuous fibres of the second part. Preferably the second part is provided with a slit (24) and the first part with a fitting protrusion, preferably with a bevelled end (23).