We consider a viscoelastic body occupying a smooth bounded domain Ω ⊂ R 3 under the effect of a volumic traction force g. The macroscopic displacement vector from the equilibrium configuration is denoted by u. Inertial effects are considered; hence the equation for u contains the second order term utt. On a part ΓD of the boundary of Ω, the body is anchored to a support and no displacement may occur; on a second part ΓN ⊂ ∂Ω, the body can move freely; on a third portion ΓC ⊂ ∂Ω, the body is in adhesive contact with a solid support. The boundary forces acting on ΓC due to the action of elastic stresses are responsible for delamination, i.e., progressive failure of adhesive bonds. This phenomenon is mathematically represented by a nonlinear ODE settled on ΓC and describing the evolution of the delamination order parameter z. Following the lines of a new approach outlined in [8] and based on duality methods in Sobolev-Bochner spaces, we define a suitable concept of weak solution to the resulting PDE system. Correspondingly, we prove an existence result on finite time intervals of arbitrary length.