  The pairwise quantum entanglement of sites in disordered electronic
one-dimensional systems (rings) is studied. We focus on the effect of diagonal
and off diagonal disorder on the concurrence $C_{ij}$ between electrons on
neighbor and non neighbor sites $i,j$ as a function of band filling. In the
case of diagonal disorder, increasing the degree of disorder leads to a
decrease of the concurrence with respect to the ordered case. However,
off-diagonal disorder produces a surprisingly strong enhancement of
entanglement. This remarkable effect occurs near half filling, where the
concurrence becomes up to 15% larger than in the ordered system.
