The structures of eight related thio(semi)carbazones are described. These are syn,1E-2-acetylpyrazine-3-thiosemicarbazone (1), syn,1E,4Z-2-acetylpyrazine-4-ethyl-3-thiosemicarbazone, (2) and syn,1Z-2-acetylpyrazine-4,4-dimethyl-3-thiosemicarbazone (3), syn,1E,4Z-2-acetylthiazole-4-phenyl-3-thiosemicarbazone (4), syn,1Z-phenyl-4,4-dimethyl-3-thiosemicarbazone (5), syn,1E,4Z-phenyl-4-methyl-3-thiosemicarbazone (6), syn,1E,4Z-phenyl-4-ethyl-3-thiosemicarbazone (7), syn,1E,4Z-2-acetophenone-5-(N-aminothionyl)-3-thiocarbazone (8). Crystal data: for 1: triclinic, P-1, a = 5.4053(10) A, b = 7.435(3) A, c = 11.772(4) A, α = 81.70(3)°, β = 82.59(2)°, γ = 77.38(2)°, and Z = 2: for 2: triclinic, P-1, a = 7.322(3) A, b = 7.8239(16) A, c = 9.783(4) A, α = 87.73(2)°, β = 79.46(3)°, γ = 80.41(2)°, and Z = 2; for 3: orthorhombic, Pnma, a = 13.5210(15) A, b = 6.6914(5) A, c = 11.7214(10) A, and Z = 4; for 4: triclinic, P-1, a = 5.7058(7) A, b = 9.8776(15) A, c = 11.869(2) A, α = 76.389(12)°, β = 86.364(13)°, γ = 88.322(12)°, and Z = 2; for 5: triclinic, P-1, a = 7.5362(3) A, b = 8.6331(4) A, c = 9.8753(4) A, α = 91.401(4)°, β = 102.532(4)°, γ = 110.540(4)°, and Z = 2; for 6: monoclinic, P2(1)/c, a = 10.7178(4) A, b = 5.5866(2) A, c = 18.7647(9) A, β = 104.392(5)°, and Z = 4; for 7: monoclinic, P2(1)/c, a = 8.9557(3) A, b = 9.7418(4) A, c = 13.6864(5) A, β = 94.044(4)°, and Z = 4; for 8: triclinic, P-1, a = 9.8091(5) A, b = 10.6173(4) A, c = 16.4691(7) A, α = 75.540(4)°, β = 80.305(4)°, γ = 65.192(4)°, and Z = 4. Structures 1, 2, 4, 5, 7, and 8 form intramolecular N4–H···N1 hydrogen-bonds. Structures 3 and 5 exist in the tautomeric form in which N1 is protonated. Structures of thio(semi)carbazones were found to fall into two categories: those with intramolecular N4-H…N1 hydrogen-bonds, and those which show a tautomeric form in which N1 is protonated.