Optical spectroscopy has been used to study the interaction of lithium impurity atoms with neutron‐produced defects in silicon. In addition to the divacancy‐associated defect absorption bands at 1.8, 3.46, and 3.61 &mgr;, several additional radiation‐produced infrared absorption bands at 1.36, 1.50, 1.6, 1.94, 2.05, 2.09, 2.14, and 2.4 &mgr; are observed in lithium‐doped silicon, irrespective of the oxygen concentration. In high oxygen concentration Si, a decrease of the (LiO)+vibrational band (9.85 &mgr;) accompanied by an increase of the oxygen interstitial vibrational band (9 &mgr;) is observed after neutron irradiation (at∼ 300 ∘K) and heat treatment (to∼ 150 ∘C). This fact rules out the possibility of the formation of the Li&sngbnd;O‐vacancy defect complex. The presence of Li decreases the production of the oxygen‐vacancy complex. The intensity and the annealing temperature of the divacancy‐associated bands strongly depend upon the Li concentration, and the intensity is found to be substantially lower than that observed for Si not containing Li. The Li defect bands exhibit a saturation in their intensity for (Li) ≈6×1016cm−3. The bands increase in intensity afterT ≳80 ∘Cheat treatment. This is attributed to the dissociation of other simple Li‐associated defects. The results indicate that higher‐order defect complexes are responsible for the bands and the divacancy must be directly involved in the formation of at least one of them. Detailed annealing studies are presented.