Recent results from deep-sequencing and tiling array studies indicated the existence of a large number of short, metabolically stable, non-coding RNAs. Some of these short RNAs derive from known RNA classes like snoRNA or tRNAs. There are intriguing similarities between short non-coding nuclear RNAs and oligonucleotides used to change alternative splicing events, which usually target a disease-relevant RNA. We review the current knowledge of this emerging class of RNAs and discuss evidence that some of these short RNAs could function in alternative splice site selection.