Results are reported for the space-dependent neutron spectra and tritium breeding ratio (TBR) in a proposed Li + C blanket of a deuterium-tritium fusion reactor. The multigroup diffusion equation is solved as an eigenvalue problem for three concentrations of lithium in graphite. The effect on the value of TBR of increasing the fraction of low-energy neutrons in a completely thermalized source is studied. A comparison of neutron spectra as obtained in the Li + C and 3He + C systems is also made. The results show that TBR increases with the concentration of lithium in graphite as well as with the fraction of low-energy neutrons in the source. [Essentially the same value of TBR (= 0.277) is obtained for the Li + C system with a lithium to graphite concentration of 4 x 10-2 as for a 3He + C system with a natural density of 3He.] Moreover, TBR attains an almost constant value for assembly thicknesses greater than -20 cm. Also, if a source with an increased fraction of low-energy neutrons is used, the effect is more pronounced in the 3He + C system for the range of lithium concentrations considered.