Recent studies suggest that lithium may retard pathological deterioration by inhibiting aberrant phosphorylation of tau in Alzheimer's disease (AD). Here, we describe three cases of AD who were treated with lithium for agitation. However, there was no obvious improvement either in global cognition, agitation or cerebrospinal fluid markers that were thought to reflect Alzheimer's pathology. Increased dosages of lithium were not tolerated by the patients because of adverse effects. It is likely that AD patients do not benefit from lithium therapy as an alternative choice of treatment.