By neutron activation analysis using the reaction6Li(n, α)3H the concentration of lithium in different kinds of silicon (Gzochralski, float zone refined and neutron transmutation doped silicon, respectively) was determined. About 1015atoms/ cm3has been found. Especially regions in which electrically active lithium up to 1014atoms Li/cm3could be detected by 4.2-K-photoluminescencespeclroscopy were investigated. But no essential differences with regard to the absolute concentration between such regions and regions without electrically active lithium could be found.