Sirtuins are a NAD(+)-dependent deacetylases involved in several cellular processes like e.g. transcriptional silencing, regulation of apoptosis, fat homeostasis and aging. Mammalian sirtuins are located in cytoplasm, nucleus as well as mitochondria. The sirtuins exhibit a number of intriguing biological properties and increase of their activity was correlated with several important physiological functions including regulation of glucose level, impact on angiogenesis and neuroprotection. On the other hand, results of research carried out on the sirtuins activity suggest that their overexpression could be related to Parkinson's disease, or some kind of cancer, however it was also shown that sirtuin inhibitors could be useful for the treatment of cancers by inhibition the formation of tumours and induction of apoptosis. Life span-prolonging effects have also been observed in yeast cells, nematodes and flies upon the overexpression of Sirtuin-1. Although sirtuins appeared as a Janus-faced enzymes selective modulators of their activity could be helpful in treatment of several age-related diseases.