Although the relationship between psyche and cancer dates back many centuries, and several studies were conducted on this topic during the last decades, the role of psychological factors in the development of cancer is still controversial. Although a lot of factors have been considered, attention has been focused mainly on stress, which has been evaluated also in experimental models. Generally, the results of case-control studies have been contradictory, and at times more stressfull events have been recorded in patients with benign tumors than in those with cancer. On the contrary, a higher incidence of stress-related cancers has not been documented in cohort studies. Since cancer is a genetic disease, it is difficult to hypothesize that psychological factors may permanently alter nucleotide sequence giving rise to multiple mutations needed for cancer development. At present, there is no sufficient evidence to affirm that psychological factors may contribute without doubt to cancer development.