An efficient synthesis of original 8-trifluoromethyl-7H-thiazolo[3,2-b]- and 1,2,4-triazolo[4,3-b]pyridazines is described. Starting from the 4-trifluoromethyl-4,5-dihydropyridazin-3-one, the methodology involves a five-membered ring closure, based on the reaction of a bis(electrophilic) reagent with an exocyclic heteroatom linked to position 3 and the endocyclic nitrogen at position 2 of the pyridazine nucleus.