CMS results on flavour spectroscopy

Two recents results in conventional and exotic heavy hadron spectroscopy with the CMS detector are presented and discussed. They concern the first observation of the $\Lambda_{b}^{0} \to J/\psi \, \Xi^{-} K^{+}$ decay and the observation of two, possibly exotic, near-threshold structures in the di-charmonium mass spectrum and the evidence of a third one. Both results are based on the LHC Run-2 dataset collected by CMS in the years 2016-2018 with proton-proton collisons at $\sqrt{s} = 13$ TeV.