A number of anomalies have been observed in rare B decays by the LHCb experiment indicating a potential new physics contribution. To understand the nature of these anomalies and to confirm their existence we need to have independent measurements performed by other experiments. In this seminar, I will present a new measurement of the Bs → μμ branching fraction and effective lifetime, as well as results of a search for the B0 → μμ decay. The analysis is based on proton-proton collision data collected by the CMS experiment at the 13 TeV center of mass energy during the LHC Run 2, corresponding to an integrated luminosity of 140/fb.