Abstract The crystal structures are reported of N-[2-(1-benzenesulfonyl-1H-pyrazol-3-yl)-6-methyl-phenyl]-benzenesulfonamide, 1, and N-[2-(1-toluene-4-sulfonyl-1H-pyrazol-3-yl)-6-methyl-phenyl]-benzenesulfonamide, 2: two compounds used in a recently reported antileishmania study. The crystallographic study reveals significant differences in the conformations adopted by molecules of 1 compared to those adopted by the three independent molecules of 2 in the solid state. The conformation differences between molecules of 1, on one hand, and the three molecules of 2, on the other, are not driven by steric effects within the molecular arrangements. If molecules 2 adopted the molecular conformation found for 1, severe steric interference would occur in the chains and other aggregates generated from the intermolecular contacts. As all the intermolecular interactions are of a weak nature, it is unlikely that aggregation would survive in dilute aqueous media, and hence the steric constraints on the conformations adopted in the solid state would not be in place in solution. Thus the difference in the solid state conformations offers no light on the greater activity of compound 1 compared to that of compound 2 in the antileishmania study in aqueous media.