Low-temperature emission and polarized absorption spectra have been recorded for U3+ ions diluted in Cs3Lu2Cl9 and Cs3Y2I9 host crystals. The experimental crystal-field levels were fitted to 13 parameters of a semiempirical Hamiltonian representing the combined atomic, one-electron crystal field (CF) as well as two-particle correlation crystal-field (CCF) operators. The red shift of the first f-d transitions from similar to14800 cm(-1) in the spectrum of U3+:Cs3Lu2Cl9 to as low as 11790 cm(-1) in that of U3+:Cs3Y2I9 has been attributed to an increase in the covalence of the U3+-X- bonds. Comparison of the differences in the Coulomb repulsion strength between U3+ and Er3+ ions in Cs3Lu2Cl9 and Cs3Y2I9 crystals suggests that the 5f electrons of U3+ ions are more 3d-like than 4f. The CF splitting of the H-2(9/2) and F-4(5/2) multiplets is unexpectedly larger for U3+:Cs3Y2I9 than for U3+:Cs3Lu2Cl9, which may be viewed as a result of the proximity of f-d states. For a correct description of the energy level structure of the H-2(9/2) and F-4(5/2) multiplets, the inclusion of CCF terms in the parametric Hamiltonian has proved to be essential. The larger f-f transition intensities for U3+:Cs3Y2I9 were also considered to be a consequence of the red shift of the first f-d states. The inadequacy in determination of the minor atomic parameters (other than parameters for Coulomb and spin-orbit interactions) and the insufficient inclusion of the influence of excited configuration in the applied CF Hamiltonian are assumed to be the main deficiencies preventing a better agreement between the experimental and calculated energies of CF levels.