Carton board packages are often adhesively bonded. The adhesive joint may fail due to cohesive fracture in the adhesive, interfacial fracture between the adhesive and one of the carton board surfaces, or cohesive fracture in the carton board. The failure may also be a combination of these failure modes. From previous studies, it is well known that the failure mechanism greatly impacts the integrity and mechanical behaviour of adhesive joints. To explore these matters, detailed experiments on adhesively bonded carton boards were performed using the Y-peel setup. By monitoring the joint at high magnification with a digital video camera during progressive loading, it was possible to link the mechanical behaviour of the adhesive joint to the fracture mechanisms involved in each case. It was found that the adhesive joint failures could be categorised into four main failure modes. The two (modes M1 and M2) failure modes with low toughness, i. e., low dissipative energy, failed by interfacial fracture with small permanent deformation in the adhesive and in the carton board. High dissipative energy modes (modes M3 and M4), however, involved multiple failures and final failure by delamination or tearing of the outermost carton board ply. It was found that the Y-peel equipment could be used as a tool to develop carton boards and hot melt adhesives in order to optimise the adhesive joint for certain package applications. From the force-elongation curve characteristics, it is possible to perceive when and how the adhesive joint may fail in a real package application. (C) Koninklijke Brill NV, Leiden, 2008