The discovery of microRNAs and its role as gene expression regulators in human carcinogenesis represents one of the most important scientific achievements of the last decade. More recently, other non-coding RNAs have been discovered and its implications in cancer are emerging as well, suggesting a broader than anticipated involvement of the non-coding genome in cancer. Moreover, completely new and unexpected functions for microRNAs are being revealed, leading to the identification of new anticancer molecular targets. This book represents a comprehensive guide on non-coding RNAs and cancer, spanning from its role as cancer biomarkers, to providing the most useful bioinformatic tools, to presenting some of the most relevant discoveries, which indicates how these fascinating molecules act as fine orchestrators of cancer biology.