We present a summary of recent CMS searches for additional Higgs bosons predicted in extended scalar-sector models.
The analyses target a wide range of signatures, including low-mass diphoton resonances, exotic decays of the 125$\,$GeV Higgs boson into pairs of light pseudoscalars, heavy Higgs bosons produced in association with bottom quarks and decaying to $b\bar b$, and the cascade process $A \to ZH \to \ell\ell t\bar t$.
The searches use up to 138$\,$fb$^{-1}$ of proton--proton collision data at $\sqrt{s}=13\,$TeV.
In all channels, the observed data are consistent with Standard Model expectations, and upper limits are set on the relevant production cross sections and branching fractions.
The results provide stringent constraints on Two-Higgs-Doublet Models, supersymmetric scenarios, and other extensions of the Higgs sector, and significantly enhance the sensitivity of previous CMS searches.