The invention relates to a vessel (1) provided with a deck (2) and with a device (3) for removing and/or installing a sub-structure (4) of a drilling or production platform, wherein said device comprises a supporting structure (5) which is capable of tilting movement in a direction transversely to an edge (6) of the deck (2), hoisting means (7) connected to said supporting structure for hoisting said sub-structure, and supporting means for supporting said sub-structure mainly during tilting movement of said supporting structure, wherein said supporting means are provided separately from the supporting structure and capable of tilting movement with respect to the edge of the deck.