Small nucleolar RNAs or snoRNAs, principally implicated in post-transcriptional chemical modification of other RNAs, were among the first non-coding RNA identified, together with ribosomal and transfer RNA. Lately, snoRNA have been involved in various unexpected functions, which renewed researcher's interest for these molecules. SnoRNA processing into smaller functional RNA species (sdRNA for snoRNA-derived RNA) or into miRNA (sno-miR), snoRNA mediated regulation of messenger RNA alternative splicing or snoRNA links to human disorders, including cancers, are some of the topics developed in this review.