Low-frequency isotropic Raman scattering and time-of flight neutron diffraction measurements were carried out for Li-6/Li-7 and H/D isotopically substituted *LiCl- and *LiClO4-tetrahydrofuran (*THF) solutions in order to obtain microscopic insight into solvated Li+, Li+center dot center dot center dot Cl- and Li+center dot center dot center dot ClO4- contact ion pairs formed in concentrated THE solutions. Symmetrical stretching vibrational mode of solvated Li+ in LiCl and LiClO4 solutions was observed at v = 181-184 and 140 cm(-1), respectively. The stretching-vibrational mode of Li+center dot center dot center dot Cl- and Li+ ClO4- solvated contact ion pairs formed in 4 mol % (LiCl)-Li-6-THF-h(8) and (LiCl)-Li-7-THE-h(8) solutions was found at v = 469 and 435 cm(-1), respectively. Detailed structural properties of solvated Li+ and the contact ion pairs were derived from the least-squares fitting analyses of the first-order difference function, Delta(Li)(Q), obtained from neutron diffraction measurements on Li-6/Li-7 isotopically substituted THF-d(8) solutions. It has been revealed that Li+ takes 4-fold coordination in the average local structure of Li+X-(THF)(3), X = Cl and ClO4. The nearest neighbor Li+center dot center dot center dot O(THF) distance was determined to be 2.21 +/- 0.01 angstrom and 2.07 +/- 0.01 A for 4 mol % *LiCl- and 10 mol % *LiClO4-THE-d(8) solutions, respectively. The Li+ anion distances for Li+center dot center dot center dot Cl- and Li+center dot center dot center dot O(ClO4-) contact ion pairs were determined to be 2.4 +/- 0.1 angstrom and 2.19 +/- 0.01 angstrom, respectively. The nearest neighbor Li+center dot center dot center dot THF interaction is significantly modified by the anion in the first solvation shell.