  We study the constraints implied by partial wave unitarity on new physics in
the form of spin-zero di-boson resonances at LHC. We derive the scale where the
effective description in terms of the SM supplemented by a single resonance is
expected to break down depending on the resonance mass and signal
cross-section. Likewise, we use unitarity arguments in order to set
perturbativity bounds on renormalizable UV completions of the effective
description. We finally discuss under which conditions scalar di-boson
resonance signals can be accommodated within weakly-coupled models.
