Single-colour resonance three-photon ionization of Sm atoms is studiedwithin the 542.4–581.6 nm spectral range. Wavenumber dependence of theSm+ ion yield shows more than 600 maxima of different amplitudes and shapes. Most of the resonancestructure observed is due to two-photon excitation of even-parity bound states lying in the34 713.1–40 526.7 cm−1 energy range. Fifteen new even-parity bound states have been found. Their energies andtotal momenta have been determined.