The crystal structures of closely related quinoline compounds substituted at the 2-position by a vinyl group, either including a Cl atom [2-(1-chloro-2-methylprop-1-enyl)-8-nitroquinoline, C(13)H(11)ClN(2)O(2), (I)] or not [2-(2-methylprop-1-enyl)-8-nitroquinoline, C(13)H(12)N(2)O(2), (II)], show an important deviation of the vinyl group from coplanarity with the quinoline ring system if the Cl atom is present. The nitro group is perpendicular [in (II)] or nearly so [in (I)] to the quinoline ring system. In (II), all non-H atoms except the nitro O atoms are located on a crystallographic mirror plane.