(1) 3-Formylthiachromen-4-one, C10H6O2S, M(r) = 190.22, monoclinic, P2(1)/c, a = 7.715 (10), b = 7.089 (11), c = 15.64 (4) angstrom, beta = 95.43 (16)-degrees, V = 852 (3) angstrom 3, Z = 4, D(x) = 1.484 g cm-3, lambda-(Mo K-alpha) = 0.71069 angstrom, mu = 3.21 cm-1, F(000) = 391.6, room temperature, final R = 0.0574 for 747 independent reflections with \F > 3-sigma\F\. The two six-membered rings which comprise the structure are each planar and are mutually inclined at 1-degrees. The aldehyde group is almost coplanar with the heterocyclic ring to which it is attached [deviation of oxygen atom 0.057 (7) angstrom]. Bond lengths imply aromaticity confined to the benzenoid ring. (2) 3-(Chloromethyl)chromen-4-one, C10H7ClO2, M(r) = 194.62, triclinic, P1BAR, a = 6.523 (6), b = 7.044 (5), c = 10.389 (12) angstrom, alpha = 79.49 (7), beta = 71.74 (8), gamma = 75.42 (7)-degrees, V =435.9 (7) angstrom 3, Z = 2, D(x) = 1.483 g cm-3, lambda-(Mo K-alpha) = 0.71069 angstrom, mu = 3.93 cm-1, F(000) = 199.98, room temperature, final R = 0.0451 for 1164 independent reflections with \F > sigma\F\. The two six-membered rings which comprise the structure are each planar and are mutually inclined at 1-degrees. The Cl atom is not coplanar with the heterocyclic ring to which the chloromethyl substituent is attached [deviation 1.537 (2) angstrom]. Bond lengths imply aromaticity confined to the benzenoid ring.