Tools recently developed in lattice QCD open very interesting perspectives to study the properties of excited states hadrons that are often produced in experiments but are difficult to take into account in the data analyses. In this talk I will discuss 2 examples chosen in the B meson sector.

1) Studying the transition $\mathrm{B}^*{}' \rightarrow \mathrm{B}$ sheds light on the validity of QCD sum rules computations in the heavy-light sector. It was claimed in the literature that the $g_{\mathrm{D}^* \mathrm{D}\pi}$ hadronic coupling evaluated by light-cone sum rules was much closer to the experimental measurement once the contribution of radial excited states was properly included on the hadronic side of the sum rule. To check that hypothesis we have performed a lattice calculation in the static limit of Heavy Quark Effective Theory, where Heavy Quark Symmetry makes the analysis simpler but does not affect the dynamics of the cloud of light quarks and gluons that governs the process under investigation.

2) Heavy Meson Chiral Perturbation Theory is very popular to extrapolate to the chiral limit phenomenologically relevant quantities of heavy flavour physics that are computed on the lattice at unphysically large pion masses. We show that the effect of the first orbital excitation may be not negligible in chiral loops because the corresponding pionic coupling is large. Since the scalar B meson lies near the B $\pi$ threshold for our simulations set-up, we have implemented meson-meson as well as quark-antiquarks interpolating fields to disentangle the scalar B meson from the two-particle state.