The crystal structures of two brominated derivatives of 4-amino-N-butyl-1,8-naphthalenedicarboximide [alternative systematic names: 8-bromo-2-butyl-7-butylamino-1H-benzo[de]isoquinoline-1,3(2H)-dione, C20H23BrN2O2, and 7-amino-8-bromo-2-butyl-1H-benzo[de]isoquinoline-1,3(2H)-dione, C16H15BrN2O2] are reported. The N-butyl groups, which are common to both compounds, are perpendicular to the plane of the naphthalenedicarboximide ring system. The butylamino group at position 4 in (1) is in the plane of the naphthalenedicarboximide ring, with the butyl group oriented towards the peri position of the naphthalenedicarboximide ring. This arrangement results in an opening of the (ring C)-N-(butyl C) angle.