Two similar 4-nitroimidazole derivatives, 1-(2′-aminophenyl)-2-methyl-4-nitroimidazole, C10H9N3O3, and 1-(2′-hydroxyphenyl)-2-methyl-4-nitroimidazole, C10H10N4O2, crystallize with two molecules in the asymmetric unit (Z′ = 2). Packing conflicts may result from tendency towards closing hydrogen-bonded rings (dimer for amino-, and tetramer for hydroxy-derivative) and molecular stacking. These conflicts are solved in different ways in both compounds, due to the different nature of 2′-substituents, but in both cases the crystal structure involves multiple molecules in the asymmetry unit. The geometrical features of symmetry-independent molecules are similar. The nitro group is almost coplanar with the imidazole plane in amino derivative while it is significantly twisted in hydroxy-one. © 2007 Elsevier B.V. All rights reserved.