  We present an extensive study of lithium abundances in dwarf components of
chromospherically active binary stars (CABS). Since most of these binaries have
known radii, masses and ages, this kind of data is especially useful for
comparisons with theoretical models which try to explain the Li depletion
phenomenon. We show that a significant part of these stars have clear Li
overabundances. These excesses are evident when comparing our sample of CABS
with binary and single stars belonging to open clusters of different ages,
namely Pleiades, Hyades, NGC752, M67 and NGC188. The Li excesses are more
conspicuous for masses in the range 0.75-0.95 Mo, indicating that the rate of
Li depletion has been less pronounced in CABS than in single stars. This
phenomenon is interpreted in the context of transport of angular momentum from
the orbit to the stellar rotation due to tidal effects. Other explanations,
however, can not be ruled out. This is the case of transport of material
induced by internal gravity waves, which could be inhibited due to the presence
of strong magnetic fields associated with the effective dynamo in CABS. The
confirmed existence of a relation between Li and fluxes in CaII H&K lines can
also be accommodated within both scenarios.
