Non-coding RNAs are a large-scale and alloplasmatic family of RNAs. According to their size, small non-coding RNAs are approximately 18-200 nt. In recent years, increasing evidence has shown that small non-coding RNAs such as tsRNA, snoRNA, snRNA and piRNA play important roles in many biological processes, and their dysregulation is closely related to cancer progression. We review the research progress in the classification, biogenesis and biological function of these. Furthermore, we highlight their dysregulation and mechanisms of action in cancer and discuss their potential as diagnostic and prognostic biomarkers or therapeutic targets. (By Dr. Lin Xiao, https://jmg.bmj.com/content/early/2022/02/09/jmedgenet-2021-108327 )