RNA interference (RNAi) is a conserved mechanism for post-transcriptional gene silencing mediated by messenger RNA (mRNA) degradation. RNAi is commonly induced by synthetic siRNA or shRNA which recognizes the targeted mRNA by base pairing and leads to target-mRNA degradation. RNAi may discriminate between two sequences only differing by one nucleotide conferring a high specificity of RNAi for its target mRNA. This property was used to develop a particular therapeutic strategy called “allele-specific-RNA interference” devoted to silence the mutated allele of genes causing dominant inherited diseases without affecting the normal allele. Therapeutic benefit was now demonstrated in cells from patients and animal models, and promising results of the first phase Ib clinical trial using siRNA-based allele-specific therapy were reported in Pachyonychia Congenita, an inherited skin disorder due to dominant mutations in the Keratin 6 gene. Our purpose is to review the successes of this strategy aiming to treat dominant inherited diseases and to highlight the pitfalls to avoid.