Cancer is an epigenetic disease, a combination of DNA modifications, chromatin organization and variations in its associated proteins, configure a new entity that regulates gene function throughout methylation, acetylation and chromatin remodelling. Irregularde novo DNA methylation, mainly promoter hypermethylation, histone deacetylation or methylation are important means for the transcriptional repression of cancer-associated genes. Reverse these epigenetic processes restoring normal expression of malignancy-preventing-genes has consequently become a new therapeutic target in cancer treatment. Aberrant patterns of epigenetic modifications will be, in a near future, crucial parameters in cancer diagnosis, prognosis and therapy.