Angle-resolved photoemission spectra (ARPES) and angle-resolved inverse photoemission spectra from single crystals of CeSn[subscript]3 (111) and LaSn[subscript]3 (111) were measured and discussed. The results were compared with the calculated band structures and fitted by the Gunnarsson-Schonhammer (G-S) model. The two-peak structure from the resonance photoemission of CeSn[subscript]3 was fitted by G-S model well by placing the single f-level at 2.0 eV below the Fermi energy before hybridization. ARPES from both CeSn[subscript]3 and LaSn[subscript]3 showed a peak near the Fermi energy without noticeable dispersion. In LaSn[subscript]3, the experimental E([vector] k) points below 1.5 eV binding energy from the band mapping agreed well with the calculated band structure;In inverse photoemission, the spectra of both CeSn[subscript]3 and LaSn[subscript]3 were totally different from the BIS spectra and gave poor agreement with the band calculations. The results suggested that there were atomic-like 4f states near the Fermi Oil, Gas, and Energy;The surface stoichiometry for CeSn[subscript]3 was measured by AES and the structure was investigated by LEED. The stoichiometry of the CeSn[subscript]3 (111) surface was close to that of the bulk, and 3-fold-symmetric LEED patterns from both CeSn[subscript]3 and LaSn[subscript]3 were observed.