The present invention relates to a process for hydrocyanating a hydrocarbon-based compound containing at least one ethylenic unsaturation by reaction in liquid medium with hydrogen cyanide in the presence of a catalyst comprising a metal element chosen from transition metals and an organophosphorus ligand, characterized in that the organophosphorus ligand is a monodentate organophosphorus compound. The present invention is in particular useful for the synthesis of adiponitrile from butadiene.