Metamemory is a multifaceted concept, which deals with an individual's knowledge and control of his or her own memory system. The ability to monitor memory performance accurately was examined in 16 patients with Alzheimer's disease (AD), 6 patients with frontotemporal lobe dementia (FTD) and 16 elderly subjects. Participants made global memory predictions in a single experimental task, both prior to and after studying 20 critical cue-target words. Prediction accuracy was evaluated with traditional score-difference measures. Our data showed that in the case of the after-study prediction FTD patients were more inaccurate in predicting their memory performance than were the AD patients, suggesting that FTD patients were more impaired than AD patients in monitoring their memory performance. Nevertheless, there seems to be no difference regarding their metacognitive knowledge or beliefs of their own memory, as indicated by the absence of difference in prediction accuracy made before study. Moreover, analyses of covariance showed that the difference in metamemory performance between AD and FTD may be related to the executive differences observed in these two populations. In sum, our results suggest that metamemory evaluation could be useful to distinguish between patients with AD and those with FTD.