Lithium–indium diselenide (LiInSe2) is a new semiconductor material, sensitive to the thermal neutrons. LiInSe2 compound was synthesized from Li (99.99%), In (99.999%) and Se (99.999%). The growth of LiInSe2 single crystals was performed using the vertical option of Bridgman–Stockbarger method. The crystals were characterized using the electrical conductivity and optical spectroscopy methods. Stoichiometric composition of the LiInSe2 was confirmed by the high precision chemical analysis, as well as by X-ray diffraction. Compact 252Cf neutron source with the activity 6.3 × 105 n/s allowed measuring amplitude characteristics and defining the optimal operating voltage for neutron detection. Time-of-flight neutron spectra were measured at the fast pulsed research reactor IBR-2 at the Joint Institute for Nuclear Research.