High precision calculation of the isotope shift of the 3 2 S 1=2 -2 2 S 1=2 transition in lithium is presented. The wave function and matrix elements of relativistic operators are obtained by using recursion relations. Apart from the relativistic contribution, we obtain the nuclear polarizability correction for 11 Li. The resulting difference of the squared charge radii 11 Li-7 Li based on the measurements of Sánchez et al. [Phys. Rev. Lett. 96, 033002 (2006)] is r 2 ch 0:15781 fm 2 , which significantly differs from the previous evaluation.