A process of producing a hollow item by injection-moulding thermoplastic material, which has a rigid external shell and at least one soft internal portion, which uses a mould comprising a matrix, a first semi-mould including a first cavity and a second semi-mould including a second cavity counter-shaped to the matrix to reproduce a respective semi-shell of said rigid external shell. The process includes the phases of positioning at least one insert made of a soft material, constituting the soft internal portion, on the matrix; covering the insert with a connecting layer; hermetically sealing the first and second semi-moulds onto the matrix along the edges of the cavities; injecting into the space between the cavities and the connecting layer a thermoplastic material that forms the rigid external shell to create a permanent connection of the soft insert to the shell. The connecting layer substantially retains the characteristics of the soft insert.