A new method was used to obtain Eu3+-doped LaOF nanocrystals. The obtained nanocrystals were synthesized for the first time using a modified Pechini sol-gel method. The products were analyzed by X-ray powder diffraction and the Rietveld method. Optimal conditions for the synthesis were found. Luminescent properties of the tetragonal and rhombo-hedral LaOF:Eu3+ nanocrystals were investigated by collecting excitation and luminescence spectra. The most effective dopant concentrations in both hosts were found. Luminescent lifetimes were also measured. The time-resolved luminescent traces showed both a growth and a decay, which pointed to energy transfer processes between Eu3+ ions in the LaOF host. In order to explain these phenomena, an adequate mechanism has been proposed. Intensity parameters Omega(2), Omega(4) and quantum efficiencies were calculated using the Judd-Ofelt theory, allowing for an extensive study of the luminescent properties of Eu3+ ion in the LaOF matrix.