LaIrIn5 is a reference compound of the heavy-fermion superconductor CeIrIn5.The lack of f electrons in LaIrIn5 indicates that there should not be any f electron participating in the construction of its Fermi surface.Thus the electronic structure comparison between LaIrIn5 and CeIrIn5 provides a good platform to study the properties of f electrons.Here angle-resolved photoemission spectroscopy (ARPES) measurements and density functional theory (DFT) calculations are performed to study the electronic structures of LaIrIn5 and CeIrIn5.We find the valence band structures of the two materials are similar to each other,except for the absence of f bands in LaIrIn5.By analyzing the Fermi crossings of the three conduction bands of the two materials quantitatively,we find the volumes of the electron pockets α and β around the M'point become larger from LaIrIn5 to CeIrIn5,while the hole pocket γ around the F'point becomes smaller.Together with the calculation results,we confirm that this is mainly originated from the f-electron contribution,while the lattice-constant difference between LaIrIn5 and CeIrIn5 only has a finite influence.We also give a summary of the f-electron character in its related Ce-115 heavy fermion compounds.Our results may be essential for the complete microscopic understanding of the 115 compounds and the related heavy-fermion systems.